Module | ActiveSupport::Callbacks::ClassMethods |
In: |
lib/active_support/callbacks.rb
|
Defines callbacks types:
define_callbacks :validate
This macro accepts the following options:
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.
the given block or a before filter raises an error. Set this option to true to change this behavior.
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.
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.