diff options
Diffstat (limited to 'railties/guides/source/active_support_core_extensions.textile')
| -rw-r--r-- | railties/guides/source/active_support_core_extensions.textile | 95 |
1 files changed, 77 insertions, 18 deletions
diff --git a/railties/guides/source/active_support_core_extensions.textile b/railties/guides/source/active_support_core_extensions.textile index 7333a81cf9..e0b1bf6e83 100644 --- a/railties/guides/source/active_support_core_extensions.textile +++ b/railties/guides/source/active_support_core_extensions.textile @@ -20,7 +20,7 @@ Thus, after a simple require like: require 'active_support' </ruby> -objects do not even respond to +blank?+, let's see how to load its definition. +objects do not even respond to +blank?+. Let's see how to load its definition. h5. Cherry-picking a Definition @@ -42,7 +42,7 @@ h5. Loading Grouped Core Extensions The next level is to simply load all extensions to +Object+. As a rule of thumb, extensions to +SomeClass+ are available in one shot by loading +active_support/core_ext/some_class+. -Thus, if that would do, to have +blank?+ available we could just load all extensions to +Object+: +Thus, to load all extensions to +Object+ (including +blank?+): <ruby> require 'active_support/core_ext/object' @@ -432,7 +432,7 @@ h4. +require_library_or_gem+ The convenience method +require_library_or_gem+ tries to load its argument with a regular +require+ first. If it fails loads +rubygems+ and tries again. -If the first attempt is a failure and +rubygems+ can't be loaded the method raises +LoadError+. On the other hand, if +rubygems+ is available but the argument is not loadable as a gem, the method gives up and +LoadError+ is also raised. +If the first attempt is a failure and +rubygems+ can't be loaded the method raises +LoadError+. A +LoadError+ is also raised if +rubygems+ is available but the argument is not loadable as a gem. For example, that's the way the MySQL adapter loads the MySQL library: @@ -498,12 +498,12 @@ h4. Attributes h5. +alias_attribute+ -Model attributes have a reader, a writer, and a predicate. You can aliase a model attribute having the corresponding three methods defined for you in one shot. As in other aliasing methods, the new name is the first argument, and the old name is the second (my mnemonic is they go in the same order as if you did an assignment): +Model attributes have a reader, a writer, and a predicate. You can alias a model attribute having the corresponding three methods defined for you in one shot. As in other aliasing methods, the new name is the first argument, and the old name is the second (my mnemonic is they go in the same order as if you did an assignment): <ruby> class User < ActiveRecord::Base # let me refer to the email column as "login", - # much meaningful for authentication code + # possibly meaningful for authentication code alias_attribute :login, :email end </ruby> @@ -528,7 +528,7 @@ The default value can be also specified with a block, which is called in the con class User attr_accessor :name, :surname attr_accessor_with_default(:full_name) { - [name, surname].compact.join(" ") + [name, surname].compact.join(" ") } end @@ -563,7 +563,7 @@ h5. Internal Attributes When you are defining an attribute in a class that is meant to be subclassed name collisions are a risk. That's remarkably important for libraries. -Active Support defines the macros +attr_internal_reader+, +attr_internal_writer+, and +attr_internal_accessor+. They behave like their Ruby builtin +attr_*+ counterparts, except they name the underlying instance variable in a way that makes collisions less likely. +Active Support defines the macros +attr_internal_reader+, +attr_internal_writer+, and +attr_internal_accessor+. They behave like their Ruby built-in +attr_*+ counterparts, except they name the underlying instance variable in a way that makes collisions less likely. The macro +attr_internal+ is a synonym for +attr_internal_accessor+: @@ -991,7 +991,7 @@ a2.x # => 2, overridden in a2 The generation of the writer instance method can be prevented by setting the option +:instance_writer+ to false, as in <ruby> -module AcitveRecord +module ActiveRecord class Base class_attribute :table_name_prefix, :instance_writer => false self.table_name_prefix = "" @@ -1001,7 +1001,7 @@ end A model may find that option useful as a way to prevent mass-assignment from setting the attribute. -For convenience +class_attribute+ defines also an instance predicate which is the double negation of what the instance reader returns. In the examples above it would be called +x?+. +For convenience +class_attribute+ also defines an instance predicate which is the double negation of what the instance reader returns. In the examples above it would be called +x?+. NOTE: Defined in +active_support/core_ext/class/attribute.rb+ @@ -1264,7 +1264,7 @@ Active Support adds that functionality to <tt>%</tt> in previous versions of Rub NOTE: Defined in +active_support/core_ext/string/interpolation.rb+. -h4. +starts_with?+ and +ends_width?+ +h4. +starts_with?+ and +ends_with?+ Active Support defines 3rd person aliases of +String#start_with?+ and +String#end_with?+: @@ -1568,7 +1568,7 @@ The method +tableize+ is +underscore+ followed by +pluralize+. "InvoiceLine".tableize # => "invoice_lines" </ruby> -As a rule of thumb, +tableize+ returns the table name that corresponds to a given model for simple cases. The actual implementation in Active Record is not straight +tableize+ indeed, because it also demodulizes de class name and checks a few options that may affect the returned string. +As a rule of thumb, +tableize+ returns the table name that corresponds to a given model for simple cases. The actual implementation in Active Record is not straight +tableize+ indeed, because it also demodulizes the class name and checks a few options that may affect the returned string. NOTE: Defined in +active_support/core_ext/string/inflections.rb+. @@ -1868,7 +1868,7 @@ The sum of an empty collection is zero by default, but this is customizable: [].sum(1) # => 1 </ruby> -If a block is given +sum+ becomes an iterator that yields the elements of the collection and sums the returned values: +If a block is given, +sum+ becomes an iterator that yields the elements of the collection and sums the returned values: <ruby> (1..5).sum {|n| n * 2 } # => 30 @@ -1896,7 +1896,7 @@ h4. +each_with_object+ The +inject+ method offers iteration with an accumulator: <ruby> -[2, 3, 4].inject(1) {|acc, i| product*i } # => 24 +[2, 3, 4].inject(1) {|product, i| product*i } # => 24 </ruby> The block is expected to return the value for the accumulator in the next iteration, and this makes building mutable objects a bit cumbersome: @@ -1942,7 +1942,7 @@ The method +many?+ is shorthand for +collection.size > 1+: <% end %> </erb> -If an optional block is given +many?+ only takes into account those elements that return true: +If an optional block is given, +many?+ only takes into account those elements that return true: <ruby> @see_more = videos.many? {|video| video.category == params[:category]} @@ -1952,7 +1952,7 @@ NOTE: Defined in +active_support/core_ext/enumerable.rb+. h4. +exclude?+ -The predicate +exclude?+ tests whether a given object does *not* belong to the collection. It is the negation of the builtin +include?+: +The predicate +exclude?+ tests whether a given object does *not* belong to the collection. It is the negation of the built-in +include?+: <ruby> to_visit << node if visited.exclude?(node) @@ -2007,7 +2007,7 @@ User.exists?(:email => params[:email]) That syntactic sugar is used a lot in Rails to avoid positional arguments where there would be too many, offering instead interfaces that emulate named parameters. In particular it is very idiomatic to use a trailing hash for options. -If a method expects a variable number of arguments and uses <tt>*</tt> in its declaration, however, such an options hash ends up being an item of the array of arguments, where kind of loses its role. +If a method expects a variable number of arguments and uses <tt>*</tt> in its declaration, however, such an options hash ends up being an item of the array of arguments, where it loses its role. In those cases, you may give an options hash a distinguished treatment with +extract_options!+. That method checks the type of the last item of an array. If it is a hash it pops it and returns it, otherwise returns an empty hash. @@ -2190,7 +2190,7 @@ Array.wrap(0) # => [0] This method is similar in purpose to <tt>Kernel#Array</tt>, but there are some differences: -* If the argument responds to +to_ary+ the method is invoked. <tt>Kernel#Array</tt> moves on to try +to_a+ if the returned value is +nil+, but <tt>Arraw.wrap</tt> returns such a +nil+ right away. +* If the argument responds to +to_ary+ the method is invoked. <tt>Kernel#Array</tt> moves on to try +to_a+ if the returned value is +nil+, but <tt>Array.wrap</tt> returns +nil+ right away. * If the returned value from +to_ary+ is neither +nil+ nor an +Array+ object, <tt>Kernel#Array</tt> raises an exception, while <tt>Array.wrap</tt> does not, it just returns the value. * It does not call +to_a+ on the argument, though special-cases +nil+ to return an empty array. @@ -2713,6 +2713,14 @@ WARNING: The original +Range#include?+ is still the one aliased to +Range#===+. NOTE: Defined in +active_support/core_ext/range/include_range.rb+. +h4. +cover?+ + +Ruby 1.9 provides +cover?+, and Active Support defines it for previous versions as an alias for +include?+. + +The method +include?+ in Ruby 1.9 is different from the one in 1.8 for non-numeric ranges: instead of being based on comparisons between the value and the range's endpoints, it walks the range with +succ+ looking for value. This works better for ranges with holes, but it has different complexity and may not finish in some other cases. + +In Ruby 1.9 the old behavior is still available in the new +cover?+, which Active Support backports for forward compatibility. For example, Rails uses +cover?+ for ranges in +validates_inclusion_of+. + h4. +overlaps?+ The method +Range#overlaps?+ says whether any two given ranges have non-void intersection: @@ -2783,6 +2791,8 @@ h5. +Date.current+ Active Support defines +Date.current+ to be today in the current time zone. That's like +Date.today+, except that it honors the user time zone, if defined. It also defines +Date.yesterday+ and +Date.tomorrow+, and the instance predicates +past?+, +today?+, and +future?+, all of them relative to +Date.current+. +When making Date comparisons using methods which honor the user time zone, make sure to use +Date.current+ and not +Date.today+. There are cases where the user time zone might be in the future compared to the system time zone, which +Date.today+ uses by default. This means +Date.today+ may equal +Date.yesterday+. + h5. Named dates h6. +prev_year+, +next_year+ @@ -3097,7 +3107,7 @@ h5. Named Datetimes h6. +DateTime.current+ -Active Support defines +DateTime.current+ to be like +Time.now.to_datetime+, except that it honors the user time zone, if defined. It also defines instance predicates +past?+, and +future?+ relative to +DateTime.current+. +Active Support defines +DateTime.current+ to be like +Time.now.to_datetime+, except that it honors the user time zone, if defined. It also defines +DateTime.yesterday+ and +DateTime.tomorrow+, and the instance predicates +past?+, and +future?+ relative to +DateTime.current+. h5. Other Extensions @@ -3274,6 +3284,12 @@ t.advance(:seconds => 1) * If +since+ or +ago+ jump to a time that can't be expressed with +Time+ a +DateTime+ object is returned instead. +h5. +Time.current+ + +Active Support defines +Time.current+ to be today in the current time zone. That's like +Time.now+, except that it honors the user time zone, if defined. It also defines +Time.yesterday+ and +Time.tomorrow+, and the instance predicates +past?+, +today?+, and +future?+, all of them relative to +Time.current+. + +When making Time comparisons using methods which honor the user time zone, make sure to use +Time.current+ and not +Time.now+. There are cases where the user time zone might be in the future compared to the system time zone, which +Time.today+ uses by default. This means +Time.now+ may equal +Time.yesterday+. + h4. Time Constructors Active Support defines +Time.current+ to be +Time.zone.now+ if there's a user time zone defined, with fallback to +Time.now+: @@ -3359,6 +3375,49 @@ The auxiliary file is written in a standard directory for temporary files, but y NOTE: Defined in +active_support/core_ext/file/atomic.rb+. +h3. Extensions to +Logger+ + +h4. +around_[level]+ + +Takes two arguments, a +before_message+ and +after_message+ and calls the current level method on the +Logger+ instance, passing in the +before_message+, then the specified message, then the +after_message+: + +<ruby> + logger = Logger.new("log/development.log") + logger.around_info("before", "after") { |logger| logger.info("during") } +</ruby> + +h4. +silence+ + +Silences every log level lesser to the specified one for the duration of the given block. Log level orders are: debug, info, error and fatal. + +<ruby> + logger = Logger.new("log/development.log") + logger.silence(Logger::INFO) do + logger.debug("In space, no one can hear you scream.") + logger.info("Scream all you want, small mailman!") + end +</ruby> + +h4. +datetime_format=+ + +Modifies the datetime format output by the formatter class associated with this logger. If the formatter class does not have a +datetime_format+ method then this is ignored. + +<ruby> + class Logger::FormatWithTime < Logger::Formatter + cattr_accessor(:datetime_format) { "%Y%m%d%H%m%S" } + + def self.call(severity, timestamp, progname, msg) + "#{timestamp.strftime(datetime_format)} -- #{String === msg ? msg : msg.inspect}\n" + end + end + + logger = Logger.new("log/development.log") + logger.formatter = Logger::FormatWithTime + logger.info("<- is the current time") +</ruby> + +NOTE: Defined in +active_support/core_ext/logger.rb+. + h3. Extensions to +NameError+ Active Support adds +missing_name?+ to +NameError+, which tests whether the exception was raised because of the name passed as argument. |