Module ActiveSupport::Callbacks::ClassMethods
In: lib/active_support/callbacks.rb

Methods

Public Instance methods

Defines callbacks types:

  define_callbacks :validate

This macro accepts the following options:

  • :terminator - Indicates when a before filter is considered

to be halted.

  define_callbacks :validate, :terminator => "result == false"

In the example above, if any before validate callbacks returns false, other callbacks are not executed. Defaults to "false", meaning no value halts the chain.

  • :rescuable - By default, after filters are not executed if

the given block or a before filter raises an error. Set this option to true to change this behavior.

  • :scope - Indicates which methods should be executed when a class

is given as callback. Defaults to [:kind].

 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.

Reset callbacks for a given type.

Set callbacks for a previously defined callback.

Syntax:

  set_callback :save, :before, :before_meth
  set_callback :save, :after,  :after_meth, :if => :condition
  set_callback :save, :around, lambda { |r| stuff; yield; stuff }

Use skip_callback to skip any defined one.

When creating or skipping callbacks, you can specify conditions that are always the same for a given key. For instance, in Action Pack, we convert :only and :except conditions into per-key conditions.

  before_filter :authenticate, :except => "index"

becomes

  dispatch_callback :before, :authenticate, :per_key => {:unless => proc {|c| c.action_name == "index"}}

Per-Key conditions are evaluated only once per use of a given key. In the case of the above example, you would do:

  run_callbacks(:dispatch, action_name) { ... dispatch stuff ... }

In that case, each action_name would get its own compiled callback method that took into consideration the per_key conditions. This is a speed improvement for ActionPack.

Skip a previously defined callback for a given type.

[Validate]