From 5a798f094ffb31acbdeca94c12589e283c4de400 Mon Sep 17 00:00:00 2001 From: Pratik Naik Date: Thu, 1 Jan 2009 21:34:12 +0000 Subject: Regenarate html --- railties/doc/guides/html/form_helpers.html | 590 ++++++++++++++++++++++++----- railties/doc/guides/html/index.html | 10 +- 2 files changed, 499 insertions(+), 101 deletions(-) (limited to 'railties/doc/guides') diff --git a/railties/doc/guides/html/form_helpers.html b/railties/doc/guides/html/form_helpers.html index 134679b9f2..84f22d0a9c 100644 --- a/railties/doc/guides/html/form_helpers.html +++ b/railties/doc/guides/html/form_helpers.html @@ -213,6 +213,16 @@ ul#navMain {

+ Different Families of helpers +

Forms that deal with model attributes

The select tag and options
Select helpers for dealing with models
Select boxes for dealing with models
Option tags from a collection of arbitrary objects

- Miscellaneous + Date and time select boxes

File upload form
Barebones helpers
Model object helpers
Common options

+ Form builders +

Scoping out form controls with fields_for
Making custom form builders

+ File Uploads +

What gets uploaded
Dealing with Ajax

+ Parameter Names +

Basic structures
Combining them
Using form helpers

+ Complex forms +

+ Changelog +

@@ -254,7 +300,7 @@ ul#navMain {

Forms in web applications are an essential interface for user input. However, form markup can quickly become tedious to write and maintain because of form control naming and their numerous attributes. Rails deals away with these complexities by providing view helpers for generating form markup. However, since they have different use-cases, developers are required to know all the differences between similar helper methods before putting them to use.

In this guide we will:

In this guide you will:

@@ -276,11 +322,6 @@ Generate select boxes from multiple types of data; Learn what makes a file upload form different;
-
-Build complex, multi-model forms. -
-

@@ -303,7 +344,7 @@ Build complex, multi-model forms.

When called without arguments like this, it creates a form element that has the current page for action attribute and "POST" as method (some line breaks added for readability):

Sample rendering of form_tag

Sample output from form_tag

<form action="/home/index" method="post">
   <div style="margin:0;padding:0">
@@ -312,7 +353,7 @@ Build complex, multi-model forms.
   Form contents
 </form>

If you carefully observe this output, you can see that the helper generated something we didn’t specify: a div element with a hidden input inside. This is a security feature of Rails called cross-site request forgery protection and form helpers generate it for every form which action isn’t "GET" (provided that this security feature is enabled).

If you carefully observe this output, you can see that the helper generated something you didn’t specify: a div element with a hidden input inside. This is a security feature of Rails called cross-site request forgery protection and form helpers generate it for every form which action isn’t "GET" (provided that this security feature is enabled).

- +

@@ -350,10 +391,10 @@ a submit element.

Always use "GET" as the method for search forms. Benefits are many: users are able to bookmark a specific search and get back to it; browsers cache results of "GET" requests, but not "POST"; and other.

To create that, we will use form_tag, label_tag, text_field_tag and submit_tag, respectively.

To create that, you will use form_tag, label_tag, text_field_tag and submit_tag, respectively.

A basic search form

@@ -393,24 +434,24 @@ a submit element. Tip

-For every form input, an ID attribute is generated from its name ("q" in our example). These IDs can be very useful for CSS styling or manipulation of form controls with JavaScript. +For every form input, an ID attribute is generated from its name ("q" in the example). These IDs can be very useful for CSS styling or manipulation of form controls with JavaScript.

1.2. Multiple hashes in form helper attributes

By now we’ve seen that the form_tag helper accepts 2 arguments: the path for the action attribute and an options hash for parameters (like :method).

Identical to the ‘link_to` helper, the path argument doesn’t have to be given as string or a named route. It can be a hash of URL parameters that Rails’ routing mechanism will turn into a valid URL. Still, we cannot simply write this:

By now you’ve seen that the form_tag helper accepts 2 arguments: the path for the action and an options hash. This hash specifies the method of form submission and HTML options such as the form element’s class.

As with the ‘link_to` helper, the path argument doesn’t have to be given a string. It can be a hash of URL parameters that Rails’ routing mechanism will turn into a valid URL. Still, you cannot simply write this:

A bad way to pass multiple hashes as method arguments

form_tag(:controller => "people", :action => "search", :method => "get")
-# => <form action="/people/search?method=get" method="post">

form_tag(:controller => "people", :action => "search", :method => "get", :class => "nifty_form")
+# => <form action="/people/search?method=get&class=nifty_form" method="post">

Here we wanted to pass two hashes, but the Ruby interpreter sees only one hash, so Rails will construct a URL that we didn’t want. The solution is to delimit the first hash (or both hashes) with curly brackets:

Here you wanted to pass two hashes, but the Ruby interpreter sees only one hash, so Rails will construct a URL with extraneous parameters. The solution is to delimit the first hash (or both hashes) with curly brackets:

The correct way of passing multiple hashes as arguments

form_tag({:controller => "people", :action => "search"}, :method => "get")
-# => <form action="/people/search" method="get">

form_tag({:controller => "people", :action => "search"}, :method => "get", :class => "nifty_form")
+# => <form action="/people/search" method="get" class="nifty_form">

This is a common pitfall when using form helpers, since many of them accept multiple hashes. So in future, if a helper produces unexpected output, make sure that you have delimited the hash parameters properly.

@@ -460,7 +501,7 @@ output: Always use labels for each checkbox and radio button. They associate text with a specific option and provide a larger clickable region.

Other form controls we might mention are the text area, password input and hidden input:

Other form controls worth mentioning are the text area, password input and hidden input:

<%= text_area_tag(:message, "Hi, nice site", :size => "24x6") %>
@@ -484,7 +525,7 @@ output:

1.4. How do forms with PUT or DELETE methods work? Rails framework encourages RESTful design of your applications, which means you’ll be making a lot of "PUT" and "DELETE" requests (besides "GET" and "POST"). Still, most browsers don’t support methods other than "GET" and "POST" when it comes to submitting forms. How does this work, then? -Rails works around this issue by emulating other methods over POST with a hidden input named "_method" that is set to reflect the wanted method: +Rails works around this issue by emulating other methods over POST with a hidden input named "_method" that is set to reflect the desired method: form_tag(search_path, :method => "put") @@ -500,9 +541,48 @@ output: When parsing POSTed data, Rails will take into account the special "_method" parameter and act as if the HTTP method was the one specified inside it ("PUT" in this example).

-2. Forms that deal with model attributes +2. Different Families of helpers -When we’re dealing with an actual model, we will use a different set of form helpers and have Rails take care of some details in the background. In the following examples we will handle an Article model. First, let us have the controller create one: +Most of Rails' form helpers are available in two forms. +2.1. Barebones helpers +These just generate the appropriate markup. These have names ending in _tag such as text_field_tag, check_box_tag. The first parameter to these is always the name of the input. This is the name under which value will appear in the params hash in the controller. For example if the form contains + + +<%= text_field_tag(:query) %> + +then the controller code should use + + +params[:query] + +to retrieve the value entered by the user. When naming inputs be aware that Rails uses certain conventions that control whether values appear at the top level of the params hash, inside an array or a nested hash and so on. You can read more about them in the parameter names section. For details on the precise usage of these helpers, please refer to the API documentation. +2.2. Model object helpers +These are designed to work with a model object (commonly an Active Record object but this need not be the case). These lack the _tag suffix, for example text_field, text_area. +For these helpers the first arguement is the name of an instance variable and the second is the name a method (usually an attribute) to call on that object. Rails will set the value of the input control to the return value of that method for the object and set an appropriate input name. If your controller has defined @person and that person’s name is Henry then a form containing: + + +<%= text_field(:person, :name) %> + +will produce output similar to + + +<input id="person_name" name="person[name]" type="text" value="Henry"/> + +Upon form submission the value entered by the user will be stored in params[:person][:name]. The params[:person] hash is suitable for passing to Person.new or, if @person is an instance of Person, @person.update_attributes. + + + + + + + +You must pass the name of an instance variable, i.e. :person or "person", not an actual instance of your model object. + + + +3. Forms that deal with model attributes + +While the helpers seen so far are handy Rails can save you some work. For example typically a form is used to edit multiple attributes of a single object, so having to repeat the name of the object being edited is clumsy. The following examples will handle an Article model. First, have the controller create one: articles_controller.rb @@ -510,11 +590,11 @@ output: @article = Article.new end -Now we switch to the view. The first thing to remember is that we should use form_for helper instead of form_tag, and that we should pass the model name and object as arguments: +Now switch to the view. The first thing to remember is to use the form_for helper instead of form_tag, and that you should pass the model name and object as arguments: articles/new.html.erb -<% form_for :article, @article, :url => { :action => "create" } do |f| %> +<% form_for :article, @article, :url => { :action => "create" }, :html => {:class => "nifty_form"} do |f| %> <%= f.text_field :title %> <%= f.text_area :body, :size => "60x12" %> <%= submit_tag "Create" %> @@ -524,12 +604,12 @@ end -:article is the name of the model and @article is our record. +:article is the name of the model and @article is the record. -The URL for the action attribute is passed as a parameter named :url. +There is a single hash of options. Routing options are passed inside :url hash, HTML options are passed in the :html hash. @@ -539,32 +619,24 @@ The form_for method yields a form builder object (the -Methods to create form controls are called on the form builder object f and without the "_tag" suffix (so text_field_tag becomes f.text_field). +Methods to create form controls are called on the form builder object f The resulting HTML is: -<form action="/articles/create" method="post"> +<form action="/articles/create" method="post" class="nifty_form"> <input id="article_title" name="article[title]" size="30" type="text" /> <textarea id="article_body" name="article[body]" cols="60" rows="12"></textarea> <input name="commit" type="submit" value="Create" /> </form> -A nice thing about f.text_field and other helper methods is that they will pre-fill the form control with the value read from the corresponding attribute in the model. For example, if we created the article instance by supplying an initial value for the title in the controller: - - -@article = Article.new(:title => "Rails makes forms easy") - -... the corresponding input will be rendered with a value: - - -<input id="post_title" name="post[title]" size="30" type="text" value="Rails makes forms easy" /> - -2.1. Relying on record identification -In the previous chapter we handled the Article model. This model is directly available to users of our application, so — following the best practices for developing with Rails — we should declare it a resource. -When dealing with RESTful resources, our calls to form_for can get significantly easier if we rely on record identification. In short, we can just pass the model instance and have Rails figure out model name and the rest: +The name passed to form_for controls where in the params hash the form values will appear. Here the name is article and so all the inputs have names of the form article[attribute_name]. Accordingly, in the create action params[:article] will be a hash with keys :title and :body. You can read more about the significance of input names in the parameter names section. +The helper methods called on the form builder are identical to the model object helpers except that it is not necessary to specify which object is being edited since this is already managed by the form builder. +3.1. Relying on record identification +In the previous chapter you handled the Article model. This model is directly available to users of our application, so — following the best practices for developing with Rails — you should declare it a resource. +When dealing with RESTful resources, calls to form_for can get significantly easier if you rely on record identification. In short, you can just pass the model instance and have Rails figure out model name and the rest: ## Creating a new article @@ -579,7 +651,8 @@ form_for(:article, @article, :url => article_path(@article), :method => "p # short-style: form_for(@article) -Notice how the short-style form_for invocation is conveniently the same, regardless of the record being new or existing. Record identification is smart enough to figure out if the record is new by asking record.new_record?. +Notice how the short-style form_for invocation is conveniently the same, regardless of the record being new or existing. Record identification is smart enough to figure out if the record is new by asking record.new_record?. It also selects the correct path to submit to and the name based on the class of the object. +Rails will also automatically set the class and id of the form appropriately: a form creating an article would have id and class new_article. If you were editing the article with id 23 the class would be set to edit_article and the id to edit_article_23. The attributes will be omitted or brevity in the rest of this guide. @@ -588,8 +661,20 @@ form_for(@article) When you’re using STI (single-table inheritance) with your models, you can’t rely on record identification on a subclass if only their parent class is declared a resource. You will have to specify the model name, :url and :method explicitly. +3.1.1. Dealing with namespaces +If you have created namespaced routes form_for has a nifty shorthand for that too. If your application has an admin namespace then + + +form_for [:admin, @article] + +will create a form that submits to the articles controller inside the admin namespace (submitting to admin_article_path(@article) in the case of an update). If you have several levels of namespacing then the syntax is similar: + + +form_for [:admin, :management, @article] + +For more information on Rails' routing system and the associated conventions, please see the routing guide. -3. Making select boxes with ease +4. Making select boxes with ease Select boxes in HTML require a significant amount of markup (one OPTION element for each option to choose from), therefore it makes the most sense for them to be dynamically generated from data stored in arrays or hashes. Here is what our wanted markup might look like: @@ -602,14 +687,14 @@ form_for(@article) <option value="12">Berlin</option> </select> -Here we have a list of cities where their names are presented to the user, but internally we want to handle just their IDs so we keep them in value attributes. Let’s see how Rails can help out here. -3.1. The select tag and options +Here you have a list of cities where their names are presented to the user, but internally the application only wants to handle their IDs so they are used as the options' value attributes. Let’s see how Rails can help out here. +4.1. The select tag and options The most generic helper is select_tag, which — as the name implies — simply generates the SELECT tag that encapsulates an options string: <%= select_tag(:city_id, '<option value="1">Lisabon</option>...') %> -This is a start, but it doesn’t dynamically create our option tags. We can generate option tags with the options_for_select helper: +This is a start, but it doesn’t dynamically create our option tags. You can generate option tags with the options_for_select helper: <%= options_for_select([['Lisabon', 1], ['Madrid', 2], ...]) %> @@ -620,16 +705,16 @@ output: <option value="2">Madrid</option> ... -For input data we used a nested array where each item has two elements: option text (city name) and option value (city id). +For input data you use a nested array where each element has two elements: option text (city name) and option value (city id). The option value is what will get submitted to your controller. It is often true that the option value is the id of a corresponding database object but this does not have to be the case. Knowing this, you can combine select_tag and options_for_select to achieve the desired, complete markup: <%= select_tag(:city_id, options_for_select(...)) %> -Sometimes, depending on our application’s needs, we also wish a specific option to be pre-selected. The options_for_select helper supports this with an optional second argument: +Sometimes, depending on an application’s needs, you also wish a specific option to be pre-selected. The options_for_select helper supports this with an optional second argument: -<%= options_for_select(cities_array, 2) %> +<%= options_for_select([['Lisabon', 1], ['Madrid', 2], ...], 2) %> output: @@ -638,9 +723,19 @@ output: ... So whenever Rails sees that the internal value of an option being generated matches this value, it will add the selected attribute to that option. -3.2. Select helpers for dealing with models -Until now we’ve covered how to make generic select boxes, but in most cases our form controls will be tied to a specific database model. So, to continue from our previous examples, let’s assume that we have a "Person" model with a city_id attribute. -Consistent with other form helpers, when dealing with models we drop the "_tag" suffix from select_tag that we used in previous examples: + + + + + + + +The second argument to options_for_select must be exactly equal to the desired internal value. In particular if the internal value is the integer 2 you cannot pass "2" to options_for_select — you must pass 2. Be aware of values extracted from the params hash as they are all strings. + + +4.2. Select boxes for dealing with models +Until now you’ve seen how to make generic select boxes, but in most cases our form controls will be tied to a specific database model. So, to continue from our previous examples, let’s assume that you have a "Person" model with a city_id attribute. +Consistent with other form helpers, when dealing with models you drop the _tag suffix from select_tag. # controller: @@ -649,83 +744,392 @@ output: # view: <%= select(:person, :city_id, [['Lisabon', 1], ['Madrid', 2], ...]) %> -Notice that the third parameter, the options array, is the same kind of argument we pass to options_for_select. One thing that we have as an advantage here is that we don’t have to worry about pre-selecting the correct city if the user already has one — Rails will do this for us by reading from @person.city_id attribute. -As before, if we were to use select helper on a form builder scoped to @person object, the syntax would be: +Notice that the third parameter, the options array, is the same kind of argument you pass to options_for_select. One advantage here is that you don’t have to worry about pre-selecting the correct city if the user already has one — Rails will do this for you by reading from the @person.city_id attribute. +As before, if you were to use select helper on a form builder scoped to @person object, the syntax would be: # select on a form builder <%= f.select(:city_id, ...) %> -3.3. Option tags from a collection of arbitrary objects -Until now we were generating option tags from nested arrays with the help of options_for_select method. Data in our array were raw values: + + + + + + + +If you are using select (or similar helpers such as collection_select, select_tag) to set a belongs_to association you must pass the name of the foreign key (in the example above city_id), not the name of association itself. If you specify city instead of `city_id Active Record will raise an error along the lines of + + +ActiveRecord::AssociationTypeMismatch: City(#17815740) expected, got Fixnum(#1138750) + +when you pass the params hash to Person.new or update_attributes. Another way of looking at this is that form helpers only edit attributes. + + +4.3. Option tags from a collection of arbitrary objects +Until now you were generating option tags from nested arrays with the help of options_for_select method. Data in our array were raw values: <%= options_for_select([['Lisabon', 1], ['Madrid', 2], ...]) %> -But what if we had a City model (perhaps an ActiveRecord one) and we wanted to generate option tags from a collection of those objects? One solution would be to make a nested array by iterating over them: +But what if you had a City model (perhaps an Active Record one) and you wanted to generate option tags from a collection of those objects? One solution would be to make a nested array by iterating over them: <% cities_array = City.find(:all).map { |city| [city.name, city.id] } %> <%= options_for_select(cities_array) %> -This is a perfectly valid solution, but Rails provides us with a less verbose alternative: options_from_collection_for_select. This helper expects a collection of arbitrary objects and two additional arguments: the names of the methods to read the option value and text from, respectively: +This is a perfectly valid solution, but Rails provides a less verbose alternative: options_from_collection_for_select. This helper expects a collection of arbitrary objects and two additional arguments: the names of the methods to read the option value and text from, respectively: <%= options_from_collection_for_select(City.all, :id, :name) %> -As the name implies, this only generates option tags. A method to go along with it is collection_select: +As the name implies, this only generates option tags. To generate a working select box you would need to use it in conjunction with select_tag, just as you would with options_for_select. A method to go along with it is collection_select: <%= collection_select(:person, :city_id, City.all, :id, :name) %> -To recap, options_from_collection_for_select are to collection_select what options_for_select are to select. -3.4. Time zone and country select -To leverage time zone support in Rails, we have to ask our users what time zone they are in. Doing so would require generating select options from a list of pre-defined TimeZone objects using collection_select, but we can simply use the time_zone_select helper that already wraps this: +To recap, options_from_collection_for_select is to collection_select what options_for_select is to select. +4.4. Time zone and country select +To leverage time zone support in Rails, you have to ask our users what time zone they are in. Doing so would require generating select options from a list of pre-defined TimeZone objects using collection_select, but you can simply use the time_zone_select helper that already wraps this: <%= time_zone_select(:person, :city_id) %> There is also time_zone_options_for_select helper for a more manual (therefore more customizable) way of doing this. Read the API documentation to learn about the possible arguments for these two methods. -When it comes to country select, Rails used to have the built-in helper country_select but was extracted to a plugin. -TODO: plugin URL +Rails used to have a country_select helper for choosing countries but this has been extracted to the country_select plugin. When using this do be aware that the exclusion or inclusion of certain names from the list can be somewhat controversial (and was the reason this functionality was extracted from rails) + +5. Date and time select boxes + +The date and time helpers differ from all the other form helpers in two important respects: + + + +Unlike other attributes you might typically have, dates and times are not representable by a single input element. Instead you have several, one for each component (year, month, day etc...). So in particular, there is no single value in your params hash with your date or time. + + + + +Other helpers use the _tag suffix to indicate whether a helper is a barebones helper or one that operates on model objects. With dates and times, select\_date, select\_time and select_datetime are the barebones helpers, date_select, time_select and datetime_select are the equivalent model object helpers + + + +Both of these families of helpers will create a series of select boxes for the different components (year, month, day etc...). +5.1. Barebones helpers +The select_* family of helpers take as their first argument an instance of Date, Time or DateTime that is used as the currently selected value. You may omit this parameter, in which case the current date is used. For example + + +<%= select_date Date::today, :prefix => :start_date %> + +outputs (with the actual option values omitted for brevity) + + +<select id="start_date_year" name="start_date[year]"> ... </select> +<select id="start_date_month" name="start_date[month]"> ... </select> +<select id="start_date_day" name="start_date[day]"> ... </select> + +The above inputs would result in params[:start_date] being a hash with keys :year, :month, :day. To get an actual Time or Date object you would have to extract these values and pass them to the appropriate constructor, for example + + +Date::civil(params[:start_date][:year].to_i, params[:start_date][:month].to_i, params[:start_date][:day].to_i) + +The :prefix option controls where in the params hash the date components will be placed. Here it was set to start_date, if omitted it will default to date. +5.2. Model object helpers +select_date does not work well with forms that update or create Active Record objects as Active Record expects each element of the params hash to correspond to one attribute. +The model object helpers for dates and times submit parameters with special names. When Active Record sees parameters with such names it knows they must be combined with the other parameters and given to a constructor appropriate to the column type. For example + + +<%= date_select :person, :birth_date %> + +outputs (with the actual option values omitted for brevity) + + +<select id="person_birth_date_1i" name="person[birth_date(1i)]"> ... </select> +<select id="person_birth_date_2i" name="person[birth_date(2i)]"> ... </select> +<select id="person_birth_date_3i" name="person[birth_date(3i)]"> ... </select> + +which results in a params hash like + + +{:person => {'birth_date(1i)' => '2008', 'birth_date(2i)' => '11', 'birth_date(3i)' => '22'}} + +When this is passed to Person.new, Active Record spots that these parameters should all be used to construct the birth_date attribute and uses the suffixed information to determine in which order it should pass these parameters to functions such as Date::civil. +5.3. Common options +Both families of helpers use the same core set of functions to generate the individual select tags and so both accept largely the same options. In particular, by default Rails will generate year options 5 years either side of the current year. If this is not an appropriate range, the :start_year and :end_year options override this. For an exhaustive list of the available options, refer to the API documentation. +As a rule of thumb you should be using date_select when working with model objects and select_date in others cases, such as a search form which filters results by date. + + + + + + + In many cases the built in date pickers are clumsy as they do not aid the user in working out the relationship between the date and the day of the week. + -4. Miscellaneous +6. Form builders -4.1. File upload form -:multipart - If set to true, the enctype is set to "multipart/form-data". -4.2. Scoping out form controls with fields_for -Creates a scope around a specific model object like form_for, but doesn’t create the form tags themselves. This makes fields_for suitable for specifying additional model objects in the same form: -4.3. Making custom form builders -You can also build forms using a customized FormBuilder class. Subclass FormBuilder and override or define some more helpers, then use your custom builder. For example, let’s say you made a helper to automatically add labels to form inputs. +As mentioned previously the object yielded by form_for and fields_for is an instance of FormBuilder (or a subclass thereof). Form builders encapsulate the notion of displaying a form elements for a single object. While you can of course write helpers for your forms in the usual way you can also subclass FormBuilder and add the helpers there. For example + + +<% form_for @person do |f| %> + <%= text_field_with_label f, :first_name %> +<% end %> + +can be replaced with -<% form_for :person, @person, :url => { :action => "update" }, :builder => LabellingFormBuilder do |f| %> +<% form_for @person, :builder => LabellingFormBuilder do |f| %> <%= f.text_field :first_name %> - <%= f.text_field :last_name %> - <%= text_area :person, :biography %> - <%= check_box_tag "person[admin]", @person.company.admin? %> <% end %> +by defining a LabellingFormBuilder class similar to the following: + + +class LabellingFormBuilder < FormBuilder + def text_field attribute, options={} + label(attribute) + text_field(attribute, options) + end +end +If you reuse this frequently you could define a labeled_form_for helper that automatically applies the :builder => LabellingFormBuilder option. +The form builder used also determines what happens when you do + + +<%= render :partial => f %> + +If f is an instance of FormBuilder then this will render the form partial, setting the partial’s object to the form builder. If the form builder is of class LabellingFormBuilder then the labelling_form partial would be rendered instead. +6.1. Scoping out form controls with fields_for +fields_for creates a form builder in exactly the same way as form_for but doesn’t create the actual <form> tags. It creates a scope around a specific model object like form_for, which is useful for specifying additional model objects in the same form. For example if you had a Person model with an associated ContactDetail model you could create a form for editing both like so: + + +<% form_for @person do |person_form| %> + <%= person_form.text_field :name %> + <% fields_for @person.contact_detail do |contact_details_form| %> + <%= contact_details_form.text_field :phone_number %> + <% end %> +<% end %> + +which produces the following output: + + +<form action="/people/1" class="edit_person" id="edit_person_1" method="post"> + <input id="person_name" name="person[name]" size="30" type="text" /> + <input id="contact_detail_phone_number" name="contact_detail[phone_number]" size="30" type="text" /> +</form> + + +7. File Uploads + +A common task is uploading some sort of file, whether it’s a picture of a person or a CSV file containing data to process. The most important thing to remember with file uploads is that the form’s encoding MUST be set to multipart/form-data. If you forget to do this the file will not be uploaded. This can be done by passing :multi_part => true as an HTML option. This means that in the case of form_tag it must be passed in the second options hash and in the case of form_for inside the :html hash. +The following two forms both upload a file. + + +<% form_tag({:action => :upload}, :multipart => true) do %> + <%= file_field_tag 'picture' %> +<% end %> + +<% form_for @person, :html => {:multipart => true} do |f| %> + <%= f.file_field :picture %> +<% end %> + +Rails provides the usual pair of helpers: the barebones file_field_tag and the model oriented file_field. The only difference with other helpers is that you cannot set a default value for file inputs as this would have no meaning. As you would expect in the first case the uploaded file is in params[:picture] and in the second case in params[:person][:picture]. +7.1. What gets uploaded +The object in the params hash is an instance of a subclass of IO. Depending on the size of the uploaded file it may in fact be a StringIO or an instance of File backed by a temporary file. In both cases the object will have an original_filename attribute containing the name the file had on the user’s computer and a content_type attribute containing the MIME type of the uploaded file. The following snippet saves the uploaded content in #{RAILS_ROOT}/public/uploads under the same name as the original file (assuming the form was the one in the previous example). + + +def upload + uploaded_io = params[:person][:picture] + File.open(Rails.root.join('public', 'uploads', uploaded_io.original_filename), 'w') do |file| + file.write(uploaded_io.read) + end +end +Once a file has been uploaded there are a multitude of potential tasks, ranging from where to store the files (on disk, Amazon S3, etc) and associating them with models to resizing image files and generating thumbnails. The intricacies of this are beyond the scope of this guide, but there are several plugins designed to assist with these. Two of the better known ones are Attachment-Fu and Paperclip. + + + + + + + If the user has not selected a file the corresponding parameter will be an empty string. + +7.2. Dealing with Ajax +Unlike other forms making an asynchronous file upload form is not as simple as replacing form_for with remote_form_for. With an AJAX form the serialization is done by javascript running inside the browser and since javascript cannot read files from your hard drive the file cannot be uploaded. The most common workaround is to use an invisible iframe that serves as the target for the form submission. + +8. Parameter Names + +As you’ve seen in the previous sections values from forms can appear either at the top level of the params hash or may appear nested in another hash. For example in a standard create +action for a Person model, params[:model] would usually be a hash of all the attributes for the person to create. The params hash can also contain arrays, arrays of hashes and so on. +Fundamentally HTML forms don’t know about any sort of structured data. All they know about is name-value pairs. Rails tacks some conventions onto parameter names which it uses to express some structure. + + + + + + + +You may find you can try out examples in this section faster by using the console to directly invoke Rails' parameter parser. For example + + +ActionController::RequestParser.parse_query_parameters "name=fred&phone=0123456789" +#=> {"name"=>"fred", "phone"=>"0123456789"} + + + +8.1. Basic structures +The two basic structures are arrays and hashes. Hashes mirror the syntax used for accessing the value in the params. For example if a form contains + + +<input id="person_name" name="person[name]" type="text" value="Henry"/> + +the params hash will contain + + +{'person' => {'name' => 'Henry'}} +and ‘params['name\’]` will retrieve the submitted value in the controller. +Hashes can be nested as many levels as required, for example + + +<input id="person_address_city" name="person[address][city]" type="text" value="New York"/> + +will result in the params hash being + + +{'person' => {'address' => {'city' => 'New York'}}} +Normally Rails ignores duplicate parameter names. If the parameter name contains [] then they will be accumulated in an array. If you wanted people to be able to input multiple phone numbers, your could place this in the form: + + +<input name="person[phone_number][]" type="text"/> +<input name="person[phone_number][]" type="text"/> +<input name="person[phone_number][]" type="text"/> + +This would result in params[:person][:phone_number] being an array. +8.2. Combining them +We can mix and match these two concepts. For example, one element of a hash might be an array as in the previous example, or you can have an array of hashes. For example a form might let you create any number of addresses by repeating the following form fragment + + +<input name="addresses[][line1]" type="text"/> +<input name="addresses[][line2]" type="text"/> +<input name="addresses[][city]" type="text"/> + +This would result in params[:addresses] being an array of hashes with keys line1, line2 and city. Rails decides to start accumulating values in a new hash whenever it encounters a input name that already exists in the current hash. +The one restriction is that although hashes can be nested arbitrarily deep then can be only one level of "arrayness". Frequently arrays can be usually replaced by hashes, for example instead of having an array of model objects one can have a hash of model objects keyed by their id. + + + + + + + Array parameters do not play well with the check_box helper. According to the HTML specification unchecked checkboxes submit no value. However it is often convenient for a checkbox to always submit a value. The check_box helper fakes this by creating a second hidden input with the same name. If the checkbox is unchecked only the hidden input is submitted. If the checkbox is checked then both are submitted but the value submitted by the checkbox takes precedence. When working with array parameters this duplicate submission will confuse Rails since duplicate input names are how it decides when to start a new hash. It is preferable to either use check_box_tag or to use hashes instead of arrays. + +8.3. Using form helpers +The previous sections did not use the Rails form helpers at all. While you can craft the input names yourself and pass them directly to helpers such as text_field_tag Rails also provides higher level support. The two tools at your disposal here are the name parameter to form_for/fields_for and the :index option. +You might want to render a form with a set of edit fields for each of a person’s addresses. Something a little like this will do the trick + + +<% form_for @person do |person_form| %> + <%= person_form.text_field :name%> + <% for address in @person.addresses %> + <% person_form.fields_for address, :index => address do |address_form|%> + <%= address_form.text_field :city %> + <% end %> + <% end %> +<% end %> + +Assuming our person had two addresses, with ids 23 and 45 this would create output similar to this: + + +<form action="/people/1" class="edit_person" id="edit_person_1" method="post"> + <input id="person_name" name="person[name]" size="30" type="text" /> + <input id="person_address_23_city" name="person[address][23][city]" size="30" type="text" /> + <input id="person_address_45_city" name="person[address][45][city]" size="30" type="text" /> +</form> + +This will result in a params hash that looks like + + +{'person' => {'name' => 'Bob', 'address' => { '23' => {'city' => 'Paris'}, '45' => {'city' => 'London'} }}} +Rails knows that all these inputs should be part of the person hash because you called fields_for on the first form builder. By specifying an :index option you’re telling rails that instead of naming the inputs person[address][city] it should insert that index surrounded by [] between the address and the city. If you pass an Active Record object as we did then Rails will call to_param on it, which by default returns the database id. This is often useful it is then easy to locate which Address record should be modified but you could pass numbers with some other significance, strings or even nil (which will result in an array parameter being created). +To create more intricate nestings, you can specify the first part of the input name (person[address] in the previous example) explicitly, for example + + +<% fields_for 'person[address][primary]', address, :index => address do |address_form| %> + <%= address_form.text_field :city %> +<% end %> + +will create inputs like + + +<input id="person_address_primary_1_city" name="person[address][primary][1][city]" size="30" type="text" value="bologna" /> + +As a general rule the final input name is the concatenation of the name given to fields_for/form_for, the index value and the name of the attribute. You can also pass an :index option directly to helpers such as text_field, but usually it is less repetitive to specify this at the form builder level rather than on individual input controls. +As a shortcut you can append [] to the name and omit the :index option. This is the same as specifing :index => address so + + +<% fields_for 'person[address][primary][]', address do |address_form| %> + <%= address_form.text_field :city %> +<% end %> + +produces exactly the same output as the previous example. + +9. Complex forms + +Many apps grow beyond simple forms editing a single object. For example when creating a Person instance you might want to allow the user to (on the same form) create multiple address records (home, work etc...). When later editing that person the user should be able to add, remove or amend addresses as necessary. While this guide has shown you all the pieces necessary to handle this, Rails does not yet have a standard end-to-end way of accomplishing this, but many have come up with viable approaches. These include: -form_for within a namespace +Ryan Bates' series of railscasts on complex forms + + + + +Handle Multiple Models in One Form from Advanced Rails Recipes + + + + +Eloy Duran’s nested_params plugin + + + + +Lance Ivy’s nested_assignment plugin and sample application + + + + +James Golick’s attribute_fu plugin + + + + +10. Changelog + +Lighthouse ticket +Authors + + +Mislav Marohnić <mislav.marohnic@gmail.com> + + + + +Frederick Cheung - - -select_tag(name, option_tags = nil, html_options = { :multiple, :disabled }) - -select(object, method, choices, options = {}, html_options = {}) -options_for_select(container, selected = nil) - -collection_select(object, method, collection, value_method, text_method, options = {}, html_options = {}) -options_from_collection_for_select(collection, value_method, text_method, selected = nil) - -time_zone_options_for_select(selected = nil, priority_zones = nil, model = ::ActiveSupport::TimeZone) -time_zone_select(object, method, priority_zones = nil, options = {}, html_options = {}) -

diff --git a/railties/doc/guides/html/index.html b/railties/doc/guides/html/index.html index 78dcf7194c..ac192f8cff 100644 --- a/railties/doc/guides/html/index.html +++ b/railties/doc/guides/html/index.html @@ -179,7 +179,7 @@ ul#navMain { - + @@ -193,13 +193,7 @@ ul#navMain { - - - - Chapters - - - + Ruby on Rails Guides -- cgit v1.2.3