module ActiveSupport::Rescuable::ClassMethods
Public Instance Methods
Rescue exceptions raised in controller actions.
rescue_from
receives a series of exception classes or class
names, and a trailing :with
option with the name of a method
or a Proc object to be called to handle them. Alternatively a block can be
given.
Handlers that take one argument will be called with the exception, so that the exception can be inspected when dealing with it.
Handlers are inherited. They are searched from right to left, from bottom
to top, and up the hierarchy. The handler of the first class for which
exception.is_a?(klass)
holds true is the one invoked, if any.
class ApplicationController < ActionController::Base rescue_from User::NotAuthorized, with: :deny_access # self defined exception rescue_from ActiveRecord::RecordInvalid, with: :show_errors rescue_from 'MyAppError::Base' do |exception| render xml: exception, status: 500 end private def deny_access ... end def show_errors(exception) exception.record.new_record? ? ... end end
Exceptions raised inside exception handlers are not propagated up.
# File lib/active_support/rescuable.rb, line 51 def rescue_from(*klasses, with: nil, &block) unless with if block_given? with = block else raise ArgumentError, "Need a handler. Pass the with: keyword argument or provide a block." end end klasses.each do |klass| key = if klass.is_a?(Module) && klass.respond_to?(:===) klass.name elsif klass.is_a?(String) klass else raise ArgumentError, "#{klass.inspect} must be an Exception class or a String referencing an Exception class" end # Put the new handler at the end because the list is read in reverse. self.rescue_handlers += [[key, with]] end end
Matches an exception to a handler based on the exception class.
If no handler matches the exception, check for a handler matching the
(optional) exception.cause. If no handler matches the exception or its
cause, this returns nil
, so you can deal with unhandled
exceptions. Be sure to re-raise unhandled exceptions if this is what you
expect.
begin … rescue => exception rescue_with_handler(exception) || raise end
Returns the exception if it was handled and nil
if it was not.
# File lib/active_support/rescuable.rb, line 88 def rescue_with_handler(exception, object: self, visited_exceptions: []) visited_exceptions << exception if handler = handler_for_rescue(exception, object: object) handler.call exception exception elsif exception if visited_exceptions.include?(exception.cause) nil else rescue_with_handler(exception.cause, object: object, visited_exceptions: visited_exceptions) end end end
Private Instance Methods
# File lib/active_support/rescuable.rb, line 137 def constantize_rescue_handler_class(class_or_name) case class_or_name when String, Symbol begin # Try a lexical lookup first since we support # # class Super # rescue_from 'Error', with: … # end # # class Sub # class Error < StandardError; end # end # # so an Error raised in Sub will hit the 'Error' handler. const_get class_or_name rescue NameError class_or_name.safe_constantize end else class_or_name end end
# File lib/active_support/rescuable.rb, line 122 def find_rescue_handler(exception) if exception # Handlers are in order of declaration but the most recently declared # is the highest priority match, so we search for matching handlers # in reverse. _, handler = rescue_handlers.reverse_each.detect do |class_or_name, _| if klass = constantize_rescue_handler_class(class_or_name) klass === exception end end handler end end