diff options
Diffstat (limited to 'guides/source/active_support_core_extensions.md')
| -rw-r--r-- | guides/source/active_support_core_extensions.md | 164 |
1 files changed, 26 insertions, 138 deletions
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md index f6f96b79c6..ff60f95a2c 100644 --- a/guides/source/active_support_core_extensions.md +++ b/guides/source/active_support_core_extensions.md @@ -1,3 +1,5 @@ +**DO NOT READ THIS FILE ON GITHUB, GUIDES ARE PUBLISHED ON http://guides.rubyonrails.org.** + Active Support Core Extensions ============================== @@ -347,7 +349,7 @@ end we get: ```ruby -current_user.to_query('user') # => user=357-john-smith +current_user.to_query('user') # => "user=357-john-smith" ``` This method escapes whatever is needed, both for the key and the value: @@ -465,7 +467,7 @@ C.new(0, 1).instance_variable_names # => ["@x", "@y"] NOTE: Defined in `active_support/core_ext/object/instance_variables.rb`. -### Silencing Warnings, Streams, and Exceptions +### Silencing Warnings and Exceptions The methods `silence_warnings` and `enable_warnings` change the value of `$VERBOSE` accordingly for the duration of their block, and reset it afterwards: @@ -473,26 +475,10 @@ The methods `silence_warnings` and `enable_warnings` change the value of `$VERBO silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", logger } ``` -You can silence any stream while a block runs with `silence_stream`: - -```ruby -silence_stream(STDOUT) do - # STDOUT is silent here -end -``` - -The `quietly` method addresses the common use case where you want to silence STDOUT and STDERR, even in subprocesses: +Silencing exceptions is also possible with `suppress`. This method receives an arbitrary number of exception classes. If an exception is raised during the execution of the block and is `kind_of?` any of the arguments, `suppress` captures it and returns silently. Otherwise the exception is not captured: ```ruby -quietly { system 'bundle install' } -``` - -For example, the railties test suite uses that one in a few places to prevent command messages from being echoed intermixed with the progress status. - -Silencing exceptions is also possible with `suppress`. This method receives an arbitrary number of exception classes. If an exception is raised during the execution of the block and is `kind_of?` any of the arguments, `suppress` captures it and returns silently. Otherwise the exception is reraised: - -```ruby -# If the user is locked the increment is lost, no big deal. +# If the user is locked, the increment is lost, no big deal. suppress(ActiveRecord::StaleObjectError) do current_user.increment! :visits end @@ -520,6 +506,8 @@ Extensions to `Module` ### `alias_method_chain` +**This method is deprecated in favour of using Module#prepend.** + Using plain Ruby you can wrap methods with other methods, that's called _alias chaining_. For example, let's say you'd like params to be strings in functional tests, as they are in real requests, but still want the convenience of assigning integers and other kind of values. To accomplish that you could wrap `ActionController::TestCase#process` this way in `test/test_helper.rb`: @@ -564,8 +552,6 @@ ActionController::TestCase.class_eval do end ``` -Rails uses `alias_method_chain` all over the code base. For example validations are added to `ActiveRecord::Base#save` by wrapping the method that way in a separate module specialized in validations. - NOTE: Defined in `active_support/core_ext/module/aliasing.rb`. ### Attributes @@ -741,7 +727,7 @@ NOTE: Defined in `active_support/core_ext/module/introspection.rb`. #### Qualified Constant Names -The standard methods `const_defined?`, `const_get` , and `const_set` accept +The standard methods `const_defined?`, `const_get`, and `const_set` accept bare constant names. Active Support extends this API to be able to pass relative qualified constant names. @@ -1011,7 +997,7 @@ self.default_params = { }.freeze ``` -They can be also accessed and overridden at the instance level. +They can also be accessed and overridden at the instance level. ```ruby A.x = 1 @@ -1251,7 +1237,7 @@ Calling `dup` or `clone` on safe strings yields safe strings. The method `remove` will remove all occurrences of the pattern: ```ruby -"Hello World".remove(/Hello /) => "World" +"Hello World".remove(/Hello /) # => "World" ``` There's also the destructive version `String#remove!`. @@ -1447,7 +1433,7 @@ Returns the substring of the string starting at position `position`: "hello".from(0) # => "hello" "hello".from(2) # => "llo" "hello".from(-2) # => "lo" -"hello".from(10) # => "" if < 1.9, nil in 1.9 +"hello".from(10) # => nil ``` NOTE: Defined in `active_support/core_ext/string/access.rb`. @@ -1950,24 +1936,6 @@ as well as adding or subtracting their results from a Time object. For example: (4.months + 5.years).from_now ``` -While these methods provide precise calculation when used as in the examples above, care -should be taken to note that this is not true if the result of `months', `years', etc is -converted before use: - -```ruby -# equivalent to 30.days.to_i.from_now -1.month.to_i.from_now - -# equivalent to 365.25.days.to_f.from_now -1.year.to_f.from_now -``` - -In such cases, Ruby's core [Date](http://ruby-doc.org/stdlib/libdoc/date/rdoc/Date.html) and -[Time](http://ruby-doc.org/stdlib/libdoc/time/rdoc/Time.html) should be used for precision -date and time arithmetic. - -NOTE: Defined in `active_support/core_ext/numeric/time.rb`. - ### Formatting Enables the formatting of numbers in a variety of ways. @@ -2214,6 +2182,17 @@ to_visit << node if visited.exclude?(node) NOTE: Defined in `active_support/core_ext/enumerable.rb`. +### `without` + +The method `without` returns a copy of an enumerable with the specified elements +removed: + +```ruby +people.without("Aaron", "Todd") +``` + +NOTE: Defined in `active_support/core_ext/enumerable.rb`. + Extensions to `Array` --------------------- @@ -3061,53 +3040,6 @@ The method `Range#overlaps?` says whether any two given ranges have non-void int NOTE: Defined in `active_support/core_ext/range/overlaps.rb`. -Extensions to `Proc` --------------------- - -### `bind` - -As you surely know Ruby has an `UnboundMethod` class whose instances are methods that belong to the limbo of methods without a self. The method `Module#instance_method` returns an unbound method for example: - -```ruby -Hash.instance_method(:delete) # => #<UnboundMethod: Hash#delete> -``` - -An unbound method is not callable as is, you need to bind it first to an object with `bind`: - -```ruby -clear = Hash.instance_method(:clear) -clear.bind({a: 1}).call # => {} -``` - -Active Support defines `Proc#bind` with an analogous purpose: - -```ruby -Proc.new { size }.bind([]).call # => 0 -``` - -As you see that's callable and bound to the argument, the return value is indeed a `Method`. - -NOTE: To do so `Proc#bind` actually creates a method under the hood. If you ever see a method with a weird name like `__bind_1256598120_237302` in a stack trace you know now where it comes from. - -Action Pack uses this trick in `rescue_from` for example, which accepts the name of a method and also a proc as callbacks for a given rescued exception. It has to call them in either case, so a bound method is returned by `handler_for_rescue`, thus simplifying the code in the caller: - -```ruby -def handler_for_rescue(exception) - _, rescuer = Array(rescue_handlers).reverse.detect do |klass_name, handler| - ... - end - - case rescuer - when Symbol - method(rescuer) - when Proc - rescuer.bind(self) - end -end -``` - -NOTE: Defined in `active_support/core_ext/proc.rb`. - Extensions to `Date` -------------------- @@ -3829,50 +3761,6 @@ WARNING. If the argument is an `IO` it needs to respond to `rewind` to be able t NOTE: Defined in `active_support/core_ext/marshal.rb`. -Extensions to `Logger` ----------------------- - -### `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") } -``` - -### `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 -``` - -### `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") -``` - -NOTE: Defined in `active_support/core_ext/logger.rb`. - Extensions to `NameError` ------------------------- @@ -3889,7 +3777,7 @@ def default_helper_module! module_name = name.sub(/Controller$/, '') module_path = module_name.underscore helper module_path -rescue MissingSourceFile => e +rescue LoadError => e raise e unless e.is_missing? "helpers/#{module_path}_helper" rescue NameError => e raise e unless e.missing_name? "#{module_name}Helper" @@ -3901,7 +3789,7 @@ NOTE: Defined in `active_support/core_ext/name_error.rb`. Extensions to `LoadError` ------------------------- -Active Support adds `is_missing?` to `LoadError`, and also assigns that class to the constant `MissingSourceFile` for backwards compatibility. +Active Support adds `is_missing?` to `LoadError`. Given a path name `is_missing?` tests whether the exception was raised due to that particular file (except perhaps for the ".rb" extension). @@ -3912,7 +3800,7 @@ def default_helper_module! module_name = name.sub(/Controller$/, '') module_path = module_name.underscore helper module_path -rescue MissingSourceFile => e +rescue LoadError => e raise e unless e.is_missing? "helpers/#{module_path}_helper" rescue NameError => e raise e unless e.missing_name? "#{module_name}Helper" |