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Source Code

# File action_controller/rescue.rb, line 218
def handler_for_rescue(exception)
  # We go from right to left because pairs are pushed onto rescue_handlers
  # as rescue_from declarations are found.
  _, handler = *rescue_handlers.reverse.detect do |klass_name, handler|
    # The purpose of allowing strings in rescue_from is to support the
    # declaration of handler associations for exception classes whose
    # definition is yet unknown.
    #
    # Since this loop needs the constants it would be inconsistent to
    # assume they should exist at this point. An early raised exception
    # could trigger some other handler and the array could include
    # precisely a string whose corresponding constant has not yet been
    # seen. This is why we are tolerant to unknown constants.
    #
    # Note that this tolerance only matters if the exception was given as
    # a string, otherwise a NameError will be raised by the interpreter
    # itself when rescue_from CONSTANT is executed.
    klass = self.class.const_get(klass_name) rescue nil
    klass ||= klass_name.constantize rescue nil
    exception.is_a?(klass) if klass
  end

  case handler
  when Symbol
    method(handler)
  when Proc
    handler.bind(self)
  end
end