define_callbacks

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.