From: "rosenfeld (Rodrigo Rosenfeld Rosas)" <rr.rosas@...>
Date: 2013-04-10T05:31:53+09:00
Subject: [ruby-core:54149] [ruby-trunk - Feature #8237] Logical method chaining via inferred receiver


Issue #8237 has been updated by rosenfeld (Rodrigo Rosenfeld Rosas).


Tom, I can't point you any references from the top of my head but I'm almost sure about reading Matz himself saying that he likes to see feature requests born from real code needs. He prefers reading real-world code before deciding if the feature is worth or not. And he doesn't seem to be the only one to think this way as I've read this statement from many more people, including me.

That's why we're suggesting you to try to find good code examples when you suggest any features. It certainly requires more thinking about the subject but it also helps you to get your features accepted when they're based on real-world requirements. When I submit new feature requests I always spend some time looking for real code in my applications where I would find that feature useful and try to use them as examples. Of course, this is just an advice and you may follow it or not, but you'll often hear complaints about your poor examples if you don't take this time.
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Feature #8237: Logical method chaining via inferred receiver
https://bugs.ruby-lang.org/issues/8237#change-38403

Author: wardrop (Tom Wardrop)
Status: Open
Priority: Normal
Assignee: 
Category: 
Target version: 


=begin
This is a feature suggestion that was raised while discussing issue #8191. The feature suggestion is to introduce some form of logical method chaining to address this reasonably common pattern:

    user && user.profile && user.profile.website && user.profile.website.thumbnail

It would be reasonably trivial to shorten this to:

    user && .profile && .website && .thumbnail

The implementation I propose would be for Ruby to allow an inferred receiver; the dot prefix would be the syntax for this. The inferred receiver would resolve to the result of the last expression in the current scope. For illustrative purposes, the following would work under this proposal:

    "some string"
    puts .upcase #=> SOME STRING

Another example:

    puts .upcase if obj.success_message || obj.error_message

    # Instead of...

    message = (obj.success_message || obj.error_message)
    puts message.upcase if message

This can also potentially provide an alternative option in syntactically awkward scenario's, such as dealing with the return value of an if statement or a catch block, avoiding the need for temporary variable assignment:

    catch :halt do
      # Do something
    end

    if .nil?
       log.info "Request was halted" 
       response.body = "Sorry, but your request could not be completed"
    end

The logical chaining scenario is the main use case however. I just wanted to demonstrate how the proposed implementation could also be used in other creative ways.

=end


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