module ActiveSupport::Rescuable::ClassMethods
Public Instance Methods
Registers exception classes with a handler to be called by rescue_with_handler
.
rescue_from
receives a series of exception classes or class names, and an exception handler specified by a trailing :with
option containing the name of a method or a Proc object. Alternatively, a block can be given as the handler.
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 rescue_from ActiveRecord::RecordInvalid, with: :show_record_errors rescue_from "MyApp::BaseError" do |exception| redirect_to root_url, alert: exception.message end private def deny_access head :forbidden end def show_record_errors(exception) redirect_back_or_to root_url, alert: exception.record.errors.full_messages.to_sentence 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