2 # Rescuable module adds support for easier exception handling.
4 def self.included(base
) # :nodoc:
5 base
.class_inheritable_accessor
:rescue_handlers
6 base
.rescue_handlers
= []
8 base
.extend(ClassMethods
)
12 # Rescue exceptions raised in controller actions.
14 # <tt>rescue_from</tt> receives a series of exception classes or class
15 # names, and a trailing <tt>:with</tt> option with the name of a method
16 # or a Proc object to be called to handle them. Alternatively a block can
19 # Handlers that take one argument will be called with the exception, so
20 # that the exception can be inspected when dealing with it.
22 # Handlers are inherited. They are searched from right to left, from
23 # bottom to top, and up the hierarchy. The handler of the first class for
24 # which <tt>exception.is_a?(klass)</tt> holds true is the one invoked, if
27 # class ApplicationController < ActionController::Base
28 # rescue_from User::NotAuthorized, :with => :deny_access # self defined exception
29 # rescue_from ActiveRecord::RecordInvalid, :with => :show_errors
31 # rescue_from 'MyAppError::Base' do |exception|
32 # render :xml => exception, :status => 500
40 # def show_errors(exception)
41 # exception.record.new_record? ? ...
44 def rescue_from(*klasses
, &block
)
45 options
= klasses
.extract_options
!
47 unless options
.has_key
?(:with)
49 options
[:with] = block
51 raise ArgumentError
, "Need a handler. Supply an options hash that has a :with key as the last argument."
55 klasses
.each
do |klass
|
56 key
= if klass
.is_a
?(Class
) && klass
<= Exception
58 elsif klass
.is_a
?(String
)
61 raise ArgumentError
, "#{klass} is neither an Exception nor a String"
64 # put the new handler at the end because the list is read in reverse
65 rescue_handlers
<< [key
, options
[:with]]
70 # Tries to rescue the exception by looking up and calling a registered handler.
71 def rescue_with_handler(exception
)
72 if handler
= handler_for_rescue(exception
)
73 handler
.arity
!= 0 ? handler
.call(exception
) : handler
.call
74 true # don't rely on the return value of the handler
78 def handler_for_rescue(exception
)
79 # We go from right to left because pairs are pushed onto rescue_handlers
80 # as rescue_from declarations are found.
81 _
, rescuer
= Array(rescue_handlers
).reverse
.detect
do |klass_name
, handler
|
82 # The purpose of allowing strings in rescue_from is to support the
83 # declaration of handler associations for exception classes whose
84 # definition is yet unknown.
86 # Since this loop needs the constants it would be inconsistent to
87 # assume they should exist at this point. An early raised exception
88 # could trigger some other handler and the array could include
89 # precisely a string whose corresponding constant has not yet been
90 # seen. This is why we are tolerant to unknown constants.
92 # Note that this tolerance only matters if the exception was given as
93 # a string, otherwise a NameError will be raised by the interpreter
94 # itself when rescue_from CONSTANT is executed.
95 klass
= self.class.const_get(klass_name
) rescue nil
96 klass
||= klass_name
.constantize
rescue nil
97 exception
.is_a
?(klass
) if klass