Module: ActiveSupport::Callbacks::ClassMethods
- Defined in:
- lib/active_support/callbacks.rb
Instance Method Summary collapse
-
#__update_callbacks(name) ⇒ Object
This is used internally to append, prepend and skip callbacks to the CallbackChain.
-
#define_callbacks(*names) ⇒ Object
Define sets of events in the object life cycle that support callbacks.
-
#normalize_callback_params(filters, block) ⇒ Object
:nodoc:.
-
#reset_callbacks(name) ⇒ Object
Remove all set callbacks for the given event.
-
#set_callback(name, *filter_list, &block) ⇒ Object
Install a callback for the given event.
-
#skip_callback(name, *filter_list, &block) ⇒ Object
Skip a previously set callback.
Instance Method Details
#__update_callbacks(name) ⇒ Object
This is used internally to append, prepend and skip callbacks to the CallbackChain.
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# File 'lib/active_support/callbacks.rb', line 565 def __update_callbacks(name) #:nodoc: ([self] + ActiveSupport::DescendantsTracker.descendants(self)).reverse_each do |target| chain = target.get_callbacks name yield target, chain.dup end end |
#define_callbacks(*names) ⇒ Object
Define sets of events in the object life cycle that support callbacks.
define_callbacks :validate
define_callbacks :initialize, :save, :destroy
Options
-
:terminator
- Determines when a before filter will halt the callback chain, preventing following before and around callbacks from being called and the event from being triggered. This should be a lambda to be executed. The current object and the result lambda of the callback will be provided to the terminator lambda.define_callbacks :validate, terminator: ->(target, result_lambda) { result_lambda.call == false }
In this example, if any before validate callbacks returns
false
, any successive before and around callback is not executed.The default terminator halts the chain when a callback throws
:abort
. -
:skip_after_callbacks_if_terminated
- Determines if after callbacks should be terminated by the:terminator
option. By default after callbacks are executed no matter if callback chain was terminated or not. This option makes sense only when:terminator
option is specified. -
:scope
- Indicates which methods should be executed when an object is used as a callback.class Audit def before(caller) puts 'Audit: before is called' end def before_save(caller) puts 'Audit: before_save is called' end end class Account include ActiveSupport::Callbacks define_callbacks :save set_callback :save, :before, Audit.new def save run_callbacks :save do puts 'save in main' end end end
In the above case whenever you save an account the method
Audit#before
will be called. On the other handdefine_callbacks :save, scope: [:kind, :name]
would trigger
Audit#before_save
instead. That’s constructed by calling#{kind}_#{name}
on the given instance. In this case “kind” is “before” and “name” is “save”. In this context:kind
and:name
have special meanings::kind
refers to the kind of callback (before/after/around) and:name
refers to the method on which callbacks are being defined.A declaration like
define_callbacks :save, scope: [:name]
would call
Audit#save
.
NOTE: method_name
passed to ‘define_model_callbacks` must not end with `!`, `?` or `=`.
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# File 'lib/active_support/callbacks.rb', line 741 def define_callbacks(*names) = names. names.each do |name| class_attribute "_#{name}_callbacks", instance_writer: false set_callbacks name, CallbackChain.new(name, ) module_eval <<-RUBY, __FILE__, __LINE__ + 1 def _run_#{name}_callbacks(&block) __run_callbacks__(_#{name}_callbacks, &block) end RUBY end end |
#normalize_callback_params(filters, block) ⇒ Object
:nodoc:
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# File 'lib/active_support/callbacks.rb', line 556 def normalize_callback_params(filters, block) # :nodoc: type = CALLBACK_FILTER_TYPES.include?(filters.first) ? filters.shift : :before = filters. filters.unshift(block) if block [type, filters, .dup] end |
#reset_callbacks(name) ⇒ Object
Remove all set callbacks for the given event.
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# File 'lib/active_support/callbacks.rb', line 656 def reset_callbacks(name) callbacks = get_callbacks name ActiveSupport::DescendantsTracker.descendants(self).each do |target| chain = target.get_callbacks(name).dup callbacks.each { |c| chain.delete(c) } target.set_callbacks name, chain end self.set_callbacks name, callbacks.dup.clear end |
#set_callback(name, *filter_list, &block) ⇒ Object
Install a callback for the given event.
set_callback :save, :before, :before_method
set_callback :save, :after, :after_method, if: :condition
set_callback :save, :around, ->(r, block) { stuff; result = block.call; stuff }
The second argument indicates whether the callback is to be run :before
, :after
, or :around
the event. If omitted, :before
is assumed. This means the first example above can also be written as:
set_callback :save, :before_method
The callback can be specified as a symbol naming an instance method; as a proc, lambda, or block; as a string to be instance evaluated(deprecated); or as an object that responds to a certain method determined by the :scope
argument to define_callbacks
.
If a proc, lambda, or block is given, its body is evaluated in the context of the current object. It can also optionally accept the current object as an argument.
Before and around callbacks are called in the order that they are set; after callbacks are called in the reverse order.
Around callbacks can access the return value from the event, if it wasn’t halted, from the yield
call.
Options
-
:if
- A symbol, a string or an array of symbols and strings, each naming an instance method or a proc; the callback will be called only when they all return a true value. -
:unless
- A symbol, a string or an array of symbols and strings, each naming an instance method or a proc; the callback will be called only when they all return a false value. -
:prepend
- Iftrue
, the callback will be prepended to the existing chain rather than appended.
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# File 'lib/active_support/callbacks.rb', line 609 def set_callback(name, *filter_list, &block) type, filters, = normalize_callback_params(filter_list, block) self_chain = get_callbacks name mapped = filters.map do |filter| Callback.build(self_chain, filter, type, ) end __update_callbacks(name) do |target, chain| [:prepend] ? chain.prepend(*mapped) : chain.append(*mapped) target.set_callbacks name, chain end end |
#skip_callback(name, *filter_list, &block) ⇒ Object
Skip a previously set callback. Like set_callback
, :if
or :unless
options may be passed in order to control when the callback is skipped.
class Writer < Person
skip_callback :validate, :before, :check_membership, if: -> { self.age > 18 }
end
An ArgumentError
will be raised if the callback has not already been set (unless the :raise
option is set to false
).
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# File 'lib/active_support/callbacks.rb', line 632 def skip_callback(name, *filter_list, &block) type, filters, = normalize_callback_params(filter_list, block) [:raise] = true unless .key?(:raise) __update_callbacks(name) do |target, chain| filters.each do |filter| callback = chain.find {|c| c.matches?(type, filter) } if !callback && [:raise] raise ArgumentError, "#{type.to_s.capitalize} #{name} callback #{filter.inspect} has not been defined" end if callback && (.key?(:if) || .key?(:unless)) new_callback = callback.(chain, if_option: [:if], unless_option: [:unless]) chain.insert(chain.index(callback), new_callback) end chain.delete(callback) end target.set_callbacks name, chain end end |