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Returning

The RewriteRails plug-in now includes its own version of #returning that overrides the #returning shipping with ActiveSupport :-o

When RewriteRails is processing source code, it turns code like this:

def registered_person(params = {})
  returning Person.new(params.merge(:registered => true)) do |person|
    if Registry.register(person)
      person.send_email_notification
    else
      person = Person.new(:default => true)
    end
  end
end

Into this:

def registered_person(params = {})
  lambda do |person|
    if Registry.register(person)
      person.send_email_notification
    else
      person = Person.new(:default => true)
    end
    person
  end.call(Person.new(params.merge(:registered => true)))
end

Note that in addition to turning the #returning "call" into a lambda that is invoked immediately, it also makes sure the new lambda returns the person variable's contents. So assignment to the variable does change what #returning appears to return.

There's more about the motivation for returning the variable's contents in my post Rewriting Returning in Rails.

Like all processors in RewriteRails, #returning is only rewritten in .rr files. Existing .rb files are not affected, including all code in the Rails framework, so it will never monkey with other people's expectations. #returning can also be disabled for a project if you don't care for it.

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RewriteRails