From 097b4678f6d52e86a9d46ba6c862e6eb6ef7bbdd Mon Sep 17 00:00:00 2001 From: Jeff Dean Date: Sun, 16 Nov 2008 20:30:42 -0500 Subject: Plugin Guide: added section on migrations, updated generator section, tightened up spacing of P's inside LI's --- railties/doc/guides/html/creating_plugins.html | 952 ++++++++++++++++--------- 1 file changed, 612 insertions(+), 340 deletions(-) (limited to 'railties/doc/guides/html/creating_plugins.html') diff --git a/railties/doc/guides/html/creating_plugins.html b/railties/doc/guides/html/creating_plugins.html index 375d216b4a..45c81f2af1 100644 --- a/railties/doc/guides/html/creating_plugins.html +++ b/railties/doc/guides/html/creating_plugins.html @@ -199,14 +199,18 @@ ul#navMain {

Chapters

  1. - Preparation + Setup +
    2. +
  2. + Tests +
  3. - Add an acts_as_yaffle method to Active Record + Add an acts_as method to Active Record
  4. - Create a generator + Models +
    5. +
  5. + Controllers +
    6. +
  6. + Helpers +
    7. +
  7. + Routes +
    8. +
  8. + Generators
  9. - Add a custom generator command -
    10. -
  10. - Add a model + Generator Commands
  11. - Add a controller -
    12. -
  12. - Add a helper + Migrations +
  13. - Add a Custom Route + Generating migrations
  14. Odds and ends @@ -388,7 +401,7 @@ A custom route method that can be used in routes.rb

    For the purpose of this guide pretend for a moment that you are an avid bird watcher. Your favorite bird is the Yaffle, and you want to create a plugin that allows other developers to share in the Yaffle goodness. First, you need to get setup for development.

    -

    1. Preparation

    +

    1. Setup

    1.1. Create the basic app

    The examples in this guide require that you have a working rails application. To create a simple rails app execute:

    @@ -448,7 +461,9 @@ create vendor/plugins/yaffle/generators/yaffle/yaffle_generator.rb create vendor/plugins/yaffle/generators/yaffle/USAGE

    To begin just change one thing - move init.rb to rails/init.rb.

    -

    1.3. Setup the plugin for testing

    + +

    2. Tests

    +

    If your plugin interacts with a database, you'll need to setup a database connection. In this guide you will learn how to test your plugin against multiple different database adapters using Active Record. This guide will not cover how to use fixtures in plugin tests.

    To setup your plugin to allow for easy testing you'll need to add 3 files:

      @@ -558,7 +573,7 @@ ENV['RAILS_ROOT end

    Now whenever you write a test that requires the database, you can call load_schema.

    -

    1.4. Run the plugin tests

    +

    2.1. Run the plugin tests

    Once you have these files in place, you can write your first test to ensure that your plugin-testing setup is correct. By default rails generates a file in vendor/plugins/yaffle/test/yaffle_test.rb with a sample test. Replace the contents of that file with:

    vendor/plugins/yaffle/test/yaffle_test.rb:

    @@ -619,7 +634,7 @@ rake DB=postgresql

    Now you are ready to test-drive your plugin!

    -

    2. Extending core classes

    +

    3. Extending core classes

    This section will explain how to add a method to String that will be available anywhere in your rails app by:

      @@ -634,7 +649,7 @@ Creating and requiring the correct files

    -

    2.1. Creating the test

    +

    3.1. Creating the test

    In this example you will add a method to String named to_squawk. To begin, create a new test file with a few assertions:

    vendor/plugins/yaffle/test/core_ext_test.rb

    @@ -665,7 +680,7 @@ NoMethodError: undefined method `to_squawk' for "Hello World":String ./test/core_ext_test.rb:5:in `test_to_squawk_prepends_the_word_squawk'

    Great - now you are ready to start development.

    -

    2.2. Organize your files

    +

    3.2. Organize your files

    A common pattern in rails plugins is to set up the file structure like this:

    @@ -712,7 +727,7 @@ http://www.gnu.org/software/src-highlite --> >> "Hello World".to_squawk => "squawk! Hello World"
    -

    2.3. Working with init.rb

    +

    3.3. Working with init.rb

    When rails loads plugins it looks for the file named init.rb. However, when the plugin is initialized, init.rb is invoked via eval (not require) so it has slightly different behavior.

    Under certain circumstances if you reopen classes or modules in init.rb you may inadvertently create a new class, rather than reopening an existing class. A better alternative is to reopen the class in a different file, and require that file from init.rb, as shown above.

    If you must reopen a class in init.rb you can use module_eval or class_eval to avoid any issues:

    @@ -742,7 +757,7 @@ http://www.gnu.org/software/src-highlite --> end -

    3. Add an acts_as_yaffle method to Active Record

    +

    4. Add an acts_as method to Active Record

    A common pattern in plugins is to add a method called acts_as_something to models. In this case, you want to write a method called acts_as_yaffle that adds a squawk method to your models.

    To begin, set up your files so that you have:

    @@ -801,7 +816,7 @@ http://www.gnu.org/software/src-highlite --> end

    With structure you can easily separate the methods that will be used for the class (like Hickwall.some_method) and the instance (like @hickwell.some_method).

    -

    3.1. Add a class method

    +

    4.1. Add a class method

    This plugin will expect that you've added a method to your model named last_squawk. However, the plugin users might have already defined a method on their model named last_squawk that they use for something else. This plugin will allow the name to be changed by adding a class method called yaffle_text_field.

    To start out, write a failing test that shows the behavior you'd like:

    vendor/plugins/yaffle/test/acts_as_yaffle_test.rb

    @@ -854,7 +869,7 @@ http://www.gnu.org/software/src-highlite --> ActiveRecord::Base.send :include, Yaffle -

    3.2. Add an instance method

    +

    4.2. Add an instance method

    This plugin will add a method named squawk to any Active Record objects that call acts_as_yaffle. The squawk method will simply set the value of one of the fields in the database.

    To start out, write a failing test that shows the behavior you'd like:

    vendor/plugins/yaffle/test/acts_as_yaffle_test.rb

    @@ -936,267 +951,7 @@ ActiveRecord::Base4. Create a generator -
    -

    Many plugins ship with generators. When you created the plugin above, you specified the —with-generator option, so you already have the generator stubs in vendor/plugins/yaffle/generators/yaffle.

    -

    Building generators is a complex topic unto itself and this section will cover one small aspect of generators: creating a generator that adds a time-stamped migration.

    -

    To create a generator you must:

    -
      -
    • -

      -Add your instructions to the manifest method of the generator -

      -
      • -
    • -

      -Add any necessary template files to the templates directory -

      -
      • -
    • -

      -Test the generator manually by running various combinations of script/generate and script/destroy -

      -
      • -
    • -

      -Update the USAGE file to add helpful documentation for your generator -

      -
      • -
    -

    4.1. Testing generators

    -

    Many rails plugin authors do not test their generators, however testing generators is quite simple. A typical generator test does the following:

    -
      -
    • -

      -Creates a new fake rails root directory that will serve as destination -

      -
      • -
    • -

      -Runs the generator forward and backward, making whatever assertions are necessary -

      -
      • -
    • -

      -Removes the fake rails root -

      -
      • -
    -

    For the generator in this section, the test could look something like this:

    -

    vendor/plugins/yaffle/test/yaffle_generator_test.rb

    -
    -
    -
    require File.dirname(__FILE__) + '/test_helper.rb'
-require 'rails_generator'
-require 'rails_generator/scripts/generate'
-require 'rails_generator/scripts/destroy'
-
-class GeneratorTest < Test::Unit::TestCase
-
-  def fake_rails_root
-    File.join(File.dirname(__FILE__), 'rails_root')
-  end
-
-  def file_list
-    Dir.glob(File.join(fake_rails_root, "db", "migrate", "*"))
-  end
-
-  def setup
-    FileUtils.mkdir_p(fake_rails_root)
-    @original_files = file_list
-  end
-
-  def teardown
-    FileUtils.rm_r(fake_rails_root)
-  end
-
-  def test_generates_correct_file_name
-    Rails::Generator::Scripts::Generate.new.run(["yaffle", "bird"], :destination => fake_rails_root)
-    new_file = (file_list - @original_files).first
-    assert_match /add_yaffle_fields_to_bird/, new_file
-  end
-
-end
-
    -

    You can run rake from the plugin directory to see this fail. Unless you are doing more advanced generator commands it typically suffices to just test the Generate script, and trust that rails will handle the Destroy and Update commands for you.

    -

    4.2. Adding to the manifest

    -

    This example will demonstrate how to use one of the built-in generator methods named migration_template to create a migration file. To start, update your generator file to look like this:

    -

    vendor/plugins/yaffle/generators/yaffle/yaffle_generator.rb

    -
    -
    -
    class YaffleGenerator < Rails::Generator::NamedBase
-  def manifest
-    record do |m|
-      m.migration_template 'migration:migration.rb', "db/migrate", {:assigns => yaffle_local_assigns,
-        :migration_file_name => "add_yaffle_fields_to_#{custom_file_name}"
-      }
-    end
-  end
-
-  private
-    def custom_file_name
-      custom_name = class_name.underscore.downcase
-      custom_name = custom_name.pluralize if ActiveRecord::Base.pluralize_table_names
-    end
-
-    def yaffle_local_assigns
-      returning(assigns = {}) do
-        assigns[:migration_action] = "add"
-        assigns[:class_name] = "add_yaffle_fields_to_#{custom_file_name}"
-        assigns[:table_name] = custom_file_name
-        assigns[:attributes] = [Rails::Generator::GeneratedAttribute.new("last_squawk", "string")]
-      end
-    end
-end
-
    -

    The generator creates a new file in db/migrate with a timestamp and an add_column statement. It reuses the built in rails migration_template method, and reuses the built-in rails migration template.

    -

    It's courteous to check to see if table names are being pluralized whenever you create a generator that needs to be aware of table names. This way people using your generator won't have to manually change the generated files if they've turned pluralization off.

    -

    4.3. Manually test the generator

    -

    To run the generator, type the following at the command line:

    -
    -
    -
    ./script/generate yaffle bird
    -
    -

    and you will see a new file:

    -

    db/migrate/20080529225649_add_yaffle_fields_to_birds.rb

    -
    -
    -
    class AddYaffleFieldsToBirds < ActiveRecord::Migration
-  def self.up
-    add_column :birds, :last_squawk, :string
-  end
-
-  def self.down
-    remove_column :birds, :last_squawk
-  end
-end
-
    -

    4.4. The USAGE file

    -

    Rails ships with several built-in generators. You can see all of the generators available to you by typing the following at the command line:

    -
    -
    -
    script/generate
    -
    -

    You should see something like this:

    -
    -
    -
    Installed Generators
-  Plugins (vendor/plugins): yaffle
-  Builtin: controller, integration_test, mailer, migration, model, observer, plugin, resource, scaffold, session_migration
    -
    -

    When you run script/generate yaffle you should see the contents of your vendor/plugins/yaffle/generators/yaffle/USAGE file.

    -

    For this plugin, update the USAGE file looks like this:

    -
    -
    -
    Description:
-    Creates a migration that adds yaffle squawk fields to the given model
-
-Example:
-    ./script/generate yaffle hickwall
-
-    This will create:
-        db/migrate/TIMESTAMP_add_yaffle_fields_to_hickwall
    -
    -
    -

    5. Add a custom generator command

    -
    -

    You may have noticed above that you can used one of the built-in rails migration commands migration_template. If your plugin needs to add and remove lines of text from existing files you will need to write your own generator methods.

    -

    This section describes how you you can create your own commands to add and remove a line of text from routes.rb. This example creates a very simple method that adds or removes a text file.

    -

    To start, add the following test method:

    -

    vendor/plugins/yaffle/test/generator_test.rb

    -
    -
    -
    def test_generates_definition
-  Rails::Generator::Scripts::Generate.new.run(["yaffle", "bird"], :destination => fake_rails_root)
-  definition = File.read(File.join(fake_rails_root, "definition.txt"))
-  assert_match /Yaffle\:/, definition
-end
-
    -

    Run rake to watch the test fail, then make the test pass add the following:

    -

    vendor/plugins/yaffle/generators/yaffle/templates/definition.txt

    -
    -
    -
    Yaffle: A bird
    -
    -

    vendor/plugins/yaffle/lib/yaffle.rb

    -
    -
    -
    require "yaffle/commands"
-
    -

    vendor/plugins/yaffle/lib/commands.rb

    -
    -
    -
    require 'rails_generator'
-require 'rails_generator/commands'
-
-module Yaffle #:nodoc:
-  module Generator #:nodoc:
-    module Commands #:nodoc:
-      module Create
-        def yaffle_definition
-          file("definition.txt", "definition.txt")
-        end
-      end
-
-      module Destroy
-        def yaffle_definition
-          file("definition.txt", "definition.txt")
-        end
-      end
-
-      module List
-        def yaffle_definition
-          file("definition.txt", "definition.txt")
-        end
-      end
-
-      module Update
-        def yaffle_definition
-          file("definition.txt", "definition.txt")
-        end
-      end
-    end
-  end
-end
-
-Rails::Generator::Commands::Create.send   :include,  Yaffle::Generator::Commands::Create
-Rails::Generator::Commands::Destroy.send  :include,  Yaffle::Generator::Commands::Destroy
-Rails::Generator::Commands::List.send     :include,  Yaffle::Generator::Commands::List
-Rails::Generator::Commands::Update.send   :include,  Yaffle::Generator::Commands::Update
-
    -

    Finally, call your new method in the manifest:

    -

    vendor/plugins/yaffle/generators/yaffle/yaffle_generator.rb

    -
    -
    -
    class YaffleGenerator < Rails::Generator::NamedBase
-  def manifest
-    m.yaffle_definition
-  end
-end
-
    -
    -

    6. Add a model

    +

    5. Models

    This section describes how to add a model named Woodpecker to your plugin that will behave the same as a model in your main app. When storing models, controllers, views and helpers in your plugin, it's customary to keep them in directories that match the rails directories. For this example, create a file structure like this:

    @@ -1271,7 +1026,7 @@ http://www.gnu.org/software/src-highlite -->

    Now your test should be passing, and you should be able to use the Woodpecker model from within your rails app, and any changes made to it are reflected immediately when running in development mode.

    -

    7. Add a controller

    +

    6. Controllers

    This section describes how to add a controller named woodpeckers to your plugin that will behave the same as a controller in your main app. This is very similar to adding a model.

    You can test your plugin's controller as you would test any other controller:

    @@ -1330,7 +1085,7 @@ http://www.gnu.org/software/src-highlite -->

    Now your test should be passing, and you should be able to use the Woodpeckers controller in your app. If you add a route for the woodpeckers controller you can start up your server and go to http://localhost:3000/woodpeckers to see your controller in action.

    -

    8. Add a helper

    +

    7. Helpers

    This section describes how to add a helper named WoodpeckersHelper to your plugin that will behave the same as a helper in your main app. This is very similar to adding a model and a controller.

    You can test your plugin's helper as you would test any other helper:

    @@ -1381,7 +1136,7 @@ http://www.gnu.org/software/src-highlite -->

    Now your test should be passing, and you should be able to use the Woodpeckers helper in your app.

    -

    9. Add a Custom Route

    +

    8. Routes

    Testing routes in plugins can be complex, especially if the controllers are also in the plugin itself. Jamis Buck showed a great example of this in http://weblog.jamisbuck.org/2006/10/26/monkey-patching-rails-extending-routes-2.

    vendor/plugins/yaffle/test/routing_test.rb

    @@ -1454,41 +1209,541 @@ http://www.gnu.org/software/src-highlite -->

    You can also see if your routes work by running rake routes from your app directory.

    -

    10. Odds and ends

    +

    9. Generators

    -

    10.1. Generate RDoc Documentation

    -

    Once your plugin is stable, the tests pass on all database and you are ready to deploy do everyone else a favor and document it! Luckily, writing documentation for your plugin is easy.

    -

    The first step is to update the README file with detailed information about how to use your plugin. A few key things to include are:

    +

    Many plugins ship with generators. When you created the plugin above, you specified the —with-generator option, so you already have the generator stubs in vendor/plugins/yaffle/generators/yaffle.

    +

    Building generators is a complex topic unto itself and this section will cover one small aspect of generators: creating a generator that adds a time-stamped migration.

    +

    To add a generator to a plugin:

    • -Your name. +Write a test

    • -How to install. +Add your instructions to the manifest method of the generator

    • -How to add the functionality to the app (several examples of common use cases). +Add any necessary template files to the templates directory

    • -Warning, gotchas or tips that might help save users time. +Update the USAGE file to add helpful documentation for your generator

    -

    Once your README is solid, go through and add rdoc comments to all of the methods that developers will use.

    -

    Before you generate your documentation, be sure to go through and add nodoc comments to those modules and methods that are not important to your users.

    -

    Once your comments are good to go, navigate to your plugin directory and run:

    -
    +

    9.1. Testing generators

    +

    Many rails plugin authors do not test their generators, however testing generators is quite simple. A typical generator test does the following:

    +
      +
    • +

      +Creates a new fake rails root directory that will serve as destination +

      +
      • +
    • +

      +Runs the generator +

      +
      • +
    • +

      +Asserts that the correct files were generated +

      +
      • +
    • +

      +Removes the fake rails root +

      +
      • +
    +

    This section will describe how to create a simple generator that adds a file. For the generator in this section, the test could look something like this:

    +

    vendor/plugins/yaffle/test/definition_generator_test.rb

    +
    +
    +
    require File.dirname(__FILE__) + '/test_helper.rb'
+require 'rails_generator'
+require 'rails_generator/scripts/generate'
+
+class DefinitionGeneratorTest < Test::Unit::TestCase
+
+  def fake_rails_root
+    File.join(File.dirname(__FILE__), 'rails_root')
+  end
+
+  def file_list
+    Dir.glob(File.join(fake_rails_root, "*"))
+  end
+
+  def setup
+    FileUtils.mkdir_p(fake_rails_root)
+    @original_files = file_list
+  end
+
+  def teardown
+    FileUtils.rm_r(fake_rails_root)
+  end
+
+  def test_generates_correct_file_name
+    Rails::Generator::Scripts::Generate.new.run(["yaffle_definition"], :destination => fake_rails_root)
+    new_file = (file_list - @original_files).first
+    assert_equal "definition.txt", File.basename(new_file)
+  end
+
+end
+
    +

    You can run rake from the plugin directory to see this fail. Unless you are doing more advanced generator commands it typically suffices to just test the Generate script, and trust that rails will handle the Destroy and Update commands for you.

    +

    To make it pass, create the generator:

    +

    vendor/plugins/yaffle/generators/yaffle_definition/yaffle_definition_generator.rb

    +
    +
    +
    class YaffleDefinitionGenerator < Rails::Generator::Base
+  def manifest
+    record do |m|
+      m.file "definition.txt", "definition.txt"
+    end
+  end
+end
+
    +

    9.2. The USAGE file

    +

    If you plan to distribute your plugin, developers will expect at least a minimum of documentation. You can add simple documentation to the generator by updating the USAGE file.

    +

    Rails ships with several built-in generators. You can see all of the generators available to you by typing the following at the command line:

    +
    +
    +
    ./script/generate
    +
    +

    You should see something like this:

    +
    +
    +
    Installed Generators
+  Plugins (vendor/plugins): yaffle_definition
+  Builtin: controller, integration_test, mailer, migration, model, observer, plugin, resource, scaffold, session_migration
    +
    +

    When you run script/generate yaffle_definition -h you should see the contents of your vendor/plugins/yaffle/generators/yaffle_definition/USAGE.

    +

    For this plugin, update the USAGE file could look like this:

    +
    +
    +
    Description:
+    Adds a file with the definition of a Yaffle to the app's main directory
    +
    +
    +

    10. Generator Commands

    +
    +

    You may have noticed above that you can used one of the built-in rails migration commands migration_template. If your plugin needs to add and remove lines of text from existing files you will need to write your own generator methods.

    +

    This section describes how you you can create your own commands to add and remove a line of text from config/routes.rb.

    +

    To start, add the following test method:

    +

    vendor/plugins/yaffle/test/route_generator_test.rb

    +
    +
    +
    require File.dirname(__FILE__) + '/test_helper.rb'
+require 'rails_generator'
+require 'rails_generator/scripts/generate'
+require 'rails_generator/scripts/destroy'
+
+class RouteGeneratorTest < Test::Unit::TestCase
+
+  def fake_rails_root
+    File.join(File.dirname(__FILE__), "rails_root")
+  end
+
+  def routes_path
+    File.join(fake_rails_root, "config", "routes.rb")
+  end
+
+  def setup
+    FileUtils.mkdir_p(File.join(fake_rails_root, "config"))
+  end
+
+  def teardown
+    FileUtils.rm_r(fake_rails_root)
+  end
+
+  def test_generates_route
+    content = <<-END
+      ActionController::Routing::Routes.draw do |map|
+        map.connect ':controller/:action/:id'
+        map.connect ':controller/:action/:id.:format'
+      end
+    END
+    File.open(routes_path, 'wb') {|f| f.write(content) }
+
+    Rails::Generator::Scripts::Generate.new.run(["yaffle_route"], :destination => fake_rails_root)
+    assert_match /map\.yaffle/, File.read(routes_path)
+  end
+
+  def test_destroys_route
+    content = <<-END
+      ActionController::Routing::Routes.draw do |map|
+        map.yaffle
+        map.connect ':controller/:action/:id'
+        map.connect ':controller/:action/:id.:format'
+      end
+    END
+    File.open(routes_path, 'wb') {|f| f.write(content) }
+
+    Rails::Generator::Scripts::Destroy.new.run(["yaffle_route"], :destination => fake_rails_root)
+    assert_no_match /map\.yaffle/, File.read(routes_path)
+  end
+end
+
    +

    Run rake to watch the test fail, then make the test pass add the following:

    +

    vendor/plugins/yaffle/lib/yaffle.rb

    +
    +
    +
    require "yaffle/commands"
+
    +

    vendor/plugins/yaffle/lib/yaffle/commands.rb

    +
    +
    +
    require 'rails_generator'
+require 'rails_generator/commands'
+
+module Yaffle #:nodoc:
+  module Generator #:nodoc:
+    module Commands #:nodoc:
+      module Create
+        def yaffle_route
+          logger.route "map.yaffle"
+          look_for = 'ActionController::Routing::Routes.draw do |map|'
+          unless options[:pretend]
+            gsub_file('config/routes.rb', /(#{Regexp.escape(look_for)})/mi){|match| "#{match}\n  map.yaffle\n"}
+          end
+        end
+      end
+
+      module Destroy
+        def yaffle_route
+          logger.route "map.yaffle"
+          gsub_file 'config/routes.rb', /\n.+?map\.yaffle/mi, ''
+        end
+      end
+
+      module List
+        def yaffle_route
+        end
+      end
+
+      module Update
+        def yaffle_route
+        end
+      end
+    end
+  end
+end
+
+Rails::Generator::Commands::Create.send   :include,  Yaffle::Generator::Commands::Create
+Rails::Generator::Commands::Destroy.send  :include,  Yaffle::Generator::Commands::Destroy
+Rails::Generator::Commands::List.send     :include,  Yaffle::Generator::Commands::List
+Rails::Generator::Commands::Update.send   :include,  Yaffle::Generator::Commands::Update
+
    +

    vendor/plugins/yaffle/generators/yaffle/yaffle_route_generator.rb

    +
    +
    +
    class YaffleRouteGenerator < Rails::Generator::Base
+  def manifest
+    record do |m|
+      m.yaffle_route
+    end
+  end
+end
+
    +

    To see this work, type:

    +
    +
    +
    ./script/generate yaffle_route
+./script/destroy yaffle_route
    +
    +
    + + + +
    +Note +If you haven't set up the custom route from above, script/destroy will fail and you'll have to remove it manually.
    +
    +
    +

    11. Migrations

    +
    +

    If your plugin requires changes to the app's database you will likely want to somehow add migrations. Rails does not include any built-in support for calling migrations from plugins, but you can still make it easy for developers to call migrations from plugins.

    +

    If you have a very simple needs, like creating a table that will always have the same name and columns, then you can use a more simple solution, like creating a custom rake task or method. If your migration needs user input to supply table names or other options, you probably want to opt for generating a migration.

    +

    Let's say you have the following migration in your plugin:

    +

    vendor/plugins/yaffle/lib/db/migrate/20081116181115_create_birdhouses.rb:

    +
    +
    +
    class CreateBirdhouses < ActiveRecord::Migration
+  def self.up
+    create_table :birdhouses, :force => true do |t|
+      t.string :name
+      t.timestamps
+    end
+  end
+
+  def self.down
+    drop_table :birdhouses
+  end
+end
+
    +

    Here are a few possibilities for how to allow developers to use your plugin migrations:

    +

    11.1. Create a custom rake task

    +

    vendor/plugins/yaffle/lib/db/migrate/20081116181115_create_birdhouses.rb:

    +
    +
    +
    class CreateBirdhouses < ActiveRecord::Migration
+  def self.up
+    create_table :birdhouses, :force => true do |t|
+      t.string :name
+      t.timestamps
+    end
+  end
+
+  def self.down
+    drop_table :birdhouses
+  end
+end
+
    +

    vendor/plugins/yaffle/tasks/yaffle.rake:

    +
    +
    +
    namespace :db do
+  namespace :migrate do
+    desc "Migrate the database through scripts in vendor/plugins/yaffle/lib/db/migrate and update db/schema.rb by invoking db:schema:dump. Target specific version with VERSION=x. Turn off output with VERBOSE=false."
+    task :yaffle => :environment do
+      ActiveRecord::Migration.verbose = ENV["VERBOSE"] ? ENV["VERBOSE"] == "true" : true
+      ActiveRecord::Migrator.migrate("vendor/plugins/yaffle/lib/db/migrate/", ENV["VERSION"] ? ENV["VERSION"].to_i : nil)
+      Rake::Task["db:schema:dump"].invoke if ActiveRecord::Base.schema_format == :ruby
+    end
+  end
+end
+
    +

    11.2. Call plugin migrations from regular migrations

    +

    vendor/plugins/yaffle/lib/yaffle.rb:

    +
    +
    +
    Dir.glob(File.join(File.dirname(__FILE__), "db", "migrate", "*")).each do |file|
+  require file
+end
+
    +

    db/migrate/20081116181115_create_birdhouses.rb:

    +
    +
    +
    class CreateBirdhouses < ActiveRecord::Migration
+  def self.up
+    Yaffle::CreateBirdhouses.up
+  end
+
+  def self.down
+    Yaffle::CreateBirdhouses.down
+  end
+end
+
    +
    + + + +
    +Note +several plugin frameworks such as Desert and Engines provide more advanced plugin functionality.
    +
    +
    +

    12. Generating migrations

    +
    +

    Generating migrations has several advantages over other methods. Namely, you can allow other developers to more easily customize the migration. The flow looks like this:

    +
      +
    • +

      +call your script/generate script and pass in whatever options they need +

      +
      • +
    • +

      +examine the generated migration, adding/removing columns or other options as necessary +

      +
      • +
    +

    This example will demonstrate how to use one of the built-in generator methods named migration_template to create a migration file. Extending the rails migration generator requires a somewhat intimate knowledge of the migration generator internals, so it's best to write a test first:

    +

    vendor/plugins/yaffle/test/yaffle_migration_generator_test.rb

    +
    +
    +
    require File.dirname(__FILE__) + '/test_helper.rb'
+require 'rails_generator'
+require 'rails_generator/scripts/generate'
+require 'rails_generator/scripts/destroy'
+
+class MigrationGeneratorTest < Test::Unit::TestCase
+
+  def fake_rails_root
+    File.join(File.dirname(__FILE__), 'rails_root')
+  end
+
+  def file_list
+    Dir.glob(File.join(fake_rails_root, "db", "migrate", "*"))
+  end
+
+  def setup
+    FileUtils.mkdir_p(fake_rails_root)
+    @original_files = file_list
+  end
+
+  def teardown
+    FileUtils.rm_r(fake_rails_root)
+  end
+
+  def test_generates_correct_file_name
+    Rails::Generator::Scripts::Generate.new.run(["yaffle", "some_name_nobody_is_likely_to_ever_use_in_a_real_migration"], :destination => fake_rails_root)
+    new_file = (file_list - @original_files).first
+    assert_match /add_yaffle_fields_to_some_name_nobody_is_likely_to_ever_use_in_a_real_migrations/, new_file
+    assert_match /add_column :some_name_nobody_is_likely_to_ever_use_in_a_real_migrations do |t|/, File.read(new_file)
+  end
+
+  def test_pluralizes_properly
+    ActiveRecord::Base.pluralize_table_names = false
+    Rails::Generator::Scripts::Generate.new.run(["yaffle", "some_name_nobody_is_likely_to_ever_use_in_a_real_migration"], :destination => fake_rails_root)
+    new_file = (file_list - @original_files).first
+    assert_match /add_yaffle_fields_to_some_name_nobody_is_likely_to_ever_use_in_a_real_migration/, new_file
+    assert_match /add_column :some_name_nobody_is_likely_to_ever_use_in_a_real_migration do |t|/, File.read(new_file)
+  end
+
+end
+
    +
    + + + +
    +Note +the migration generator checks to see if a migation already exists, and it's hard-coded to check the db/migrate directory. As a result, if your test tries to generate a migration that already exists in the app, it will fail. The easy workaround is to make sure that the name you generate in your test is very unlikely to actually appear in the app.
    +
    +

    After running the test with rake you can make it pass with:

    +

    vendor/plugins/yaffle/generators/yaffle/yaffle_generator.rb

    +
    +
    +
    class YaffleGenerator < Rails::Generator::NamedBase
+  def manifest
+    record do |m|
+      m.migration_template 'migration:migration.rb', "db/migrate", {:assigns => yaffle_local_assigns,
+        :migration_file_name => "add_yaffle_fields_to_#{custom_file_name}"
+      }
+    end
+  end
+
+  private
+    def custom_file_name
+      custom_name = class_name.underscore.downcase
+      custom_name = custom_name.pluralize if ActiveRecord::Base.pluralize_table_names
+    end
+
+    def yaffle_local_assigns
+      returning(assigns = {}) do
+        assigns[:migration_action] = "add"
+        assigns[:class_name] = "add_yaffle_fields_to_#{custom_file_name}"
+        assigns[:table_name] = custom_file_name
+        assigns[:attributes] = [Rails::Generator::GeneratedAttribute.new("last_squawk", "string")]
+      end
+    end
+end
+
    +

    The generator creates a new file in db/migrate with a timestamp and an add_column statement. It reuses the built in rails migration_template method, and reuses the built-in rails migration template.

    +

    It's courteous to check to see if table names are being pluralized whenever you create a generator that needs to be aware of table names. This way people using your generator won't have to manually change the generated files if they've turned pluralization off.

    +

    To run the generator, type the following at the command line:

    +
    +
    +
    ./script/generate yaffle_migration bird
    +
    +

    and you will see a new file:

    +

    db/migrate/20080529225649_add_yaffle_fields_to_birds.rb

    +
    +
    +
    class AddYaffleFieldsToBirds < ActiveRecord::Migration
+  def self.up
+    add_column :birds, :last_squawk, :string
+  end
+
+  def self.down
+    remove_column :birds, :last_squawk
+  end
+end
+
    +
    +

    13. Odds and ends

    +
    +

    13.1. Generate RDoc Documentation

    +

    Once your plugin is stable, the tests pass on all database and you are ready to deploy do everyone else a favor and document it! Luckily, writing documentation for your plugin is easy.

    +

    The first step is to update the README file with detailed information about how to use your plugin. A few key things to include are:

    +
      +
    • +

      +Your name. +

      +
      • +
    • +

      +How to install. +

      +
      • +
    • +

      +How to add the functionality to the app (several examples of common use cases). +

      +
      • +
    • +

      +Warning, gotchas or tips that might help save users time. +

      +
      • +
    +

    Once your README is solid, go through and add rdoc comments to all of the methods that developers will use.

    +

    Before you generate your documentation, be sure to go through and add nodoc comments to those modules and methods that are not important to your users.

    +

    Once your comments are good to go, navigate to your plugin directory and run:

    +
    rake rdoc
    -

    10.2. Write custom Rake tasks in your plugin

    +

    13.2. Write custom Rake tasks in your plugin

    When you created the plugin with the built-in rails generator, it generated a rake file for you in vendor/plugins/yaffle/tasks/yaffle.rake. Any rake task you add here will be available to the app.

    Many plugin authors put all of their rake tasks into a common namespace that is the same as the plugin, like so:

    vendor/plugins/yaffle/tasks/yaffle.rake

    @@ -1510,7 +1765,7 @@ http://www.gnu.org/software/src-highlite --> 
    yaffle:squawk             # Prints out the word 'Yaffle'

    You can add as many files as you want in the tasks directory, and if they end in .rake Rails will pick them up.

    -

    10.3. Store plugins in alternate locations

    +

    13.3. Store plugins in alternate locations

    You can store plugins wherever you want - you just have to add those plugins to the plugins path in environment.rb.

    Since the plugin is only loaded after the plugin paths are defined, you can't redefine this in your plugins - but it may be good to now.

    You can even store plugins inside of other plugins for complete plugin madness!

    @@ -1521,14 +1776,14 @@ http://www.lorenzobettini.it http://www.gnu.org/software/src-highlite --> 
    config.plugin_paths << File.join(RAILS_ROOT,"vendor","plugins","yaffle","lib","plugins")
    -

    10.4. Create your own Plugin Loaders and Plugin Locators

    +

    13.4. Create your own Plugin Loaders and Plugin Locators

    If the built-in plugin behavior is inadequate, you can change almost every aspect of the location and loading process. You can write your own plugin locators and plugin loaders, but that's beyond the scope of this tutorial.

    -

    10.5. Use Custom Plugin Generators

    +

    13.5. Use Custom Plugin Generators

    If you are an RSpec fan, you can install the rspec_plugin_generator gem, which will generate the spec folder and database for you. See http://github.com/pat-maddox/rspec-plugin-generator/tree/master.

    -

    11. Appendix

    +

    14. Appendix

    -

    11.1. References

    +

    14.1. References

    -

    11.2. Final plugin directory structure

    +

    14.2. Final plugin directory structure

    The final plugin should have a directory structure that looks something like this:

    -
      |-- MIT-LICENSE
-  |-- README
-  |-- Rakefile
-  |-- generators
-  |   `-- yaffle
-  |       |-- USAGE
-  |       |-- templates
-  |       |   `-- definition.txt
-  |       `-- yaffle_generator.rb
-  |-- init.rb
-  |-- install.rb
-  |-- lib
-  |   |-- acts_as_yaffle.rb
-  |   |-- commands.rb
-  |   |-- core_ext.rb
-  |   |-- routing.rb
-  |   `-- view_helpers.rb
-  |-- tasks
-  |   `-- yaffle_tasks.rake
-  |-- test
-  |   |-- acts_as_yaffle_test.rb
-  |   |-- core_ext_test.rb
-  |   |-- database.yml
-  |   |-- debug.log
-  |   |-- routing_test.rb
-  |   |-- schema.rb
-  |   |-- test_helper.rb
-  |   `-- view_helpers_test.rb
-  |-- uninstall.rb
-  `-- yaffle_plugin.sqlite3.db
    +
    vendor/plugins/yaffle/
+|-- MIT-LICENSE
+|-- README
+|-- Rakefile
+|-- generators
+|   `-- yaffle
+|       |-- USAGE
+|       |-- templates
+|       |   `-- definition.txt
+|       `-- yaffle_generator.rb
+|-- install.rb
+|-- lib
+|   |-- app
+|   |   |-- controllers
+|   |   |   `-- woodpeckers_controller.rb
+|   |   |-- helpers
+|   |   |   `-- woodpeckers_helper.rb
+|   |   `-- models
+|   |       `-- woodpecker.rb
+|   |-- yaffle
+|   |   |-- acts_as_yaffle.rb
+|   |   |-- commands.rb
+|   |   `-- core_ext.rb
+|   `-- yaffle.rb
+|-- rails
+|   `-- init.rb
+|-- tasks
+|   `-- yaffle_tasks.rake
+|-- test
+|   |-- acts_as_yaffle_test.rb
+|   |-- core_ext_test.rb
+|   |-- database.yml
+|   |-- debug.log
+|   |-- generator_test.rb
+|   |-- schema.rb
+|   |-- test_helper.rb
+|   |-- woodpecker_test.rb
+|   |-- woodpeckers_controller_test.rb
+|   |-- wookpeckers_helper_test.rb
+|   |-- yaffle_plugin.sqlite3.db
+|   `-- yaffle_test.rb
+`-- uninstall.rb
    -- cgit v1.2.3