instance method `define_callbacks`

Ruby on Rails 4.1.16

Since v2.2.3

Available in: v2.2.3 v2.3.18 v3.0.20 v3.1.12 v3.2.22.5 v4.0.13 v4.1.16 v4.2.9 v5.2.8.1 v6.0.6 v6.1.7.10 v7.0.10 v7.1.6 v7.2.3 v8.0.4 v8.1.2

Compare with:

define_callbacks(*names)

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 callbacks from being called and the event from being triggered. This should be a lambda to be executed. The current object and the return result of the callback will be called with the lambda.
```
define_callbacks :validate, terminator: ->(target, result) { result == false }
```
In this example, if any before validate callbacks returns false, other callbacks are not executed. Defaults to false, meaning no value halts the chain.
:skip_after_callbacks_if_terminated - Determines if after callbacks should be terminated by the :terminator option. By default after callbacks executed no matter if callback chain was terminated or not. 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 hand
```
define_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.

Parameters

names rest

Source

# File activesupport/lib/active_support/callbacks.rb, line 761
      def define_callbacks(*names)
        options = names.extract_options!
        if options.key?(:terminator) && String === options[:terminator]
          ActiveSupport::Deprecation.warn "String based terminators are deprecated, please use a lambda"
          value = options[:terminator]
          line = class_eval "lambda { |result| #{value} }", __FILE__, __LINE__
          options[:terminator] = lambda { |target, result| target.instance_exec(result, &line) }
        end

        names.each do |name|
          class_attribute "_#{name}_callbacks", instance_writer: false
          set_callbacks name, CallbackChain.new(name, options)
        end
      end

Defined in activesupport/lib/active_support/callbacks.rb line 761 · View on GitHub · Improve this page · Find usages on GitHub

Defined in ActiveSupport::Callbacks::ClassMethods

Signature

Options

Parameters