Feature #8237

Logical method chaining via inferred receiver

Added by wardrop (Tom Wardrop) over 7 years ago. Updated about 5 years ago.

Target version:


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 && &&

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

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

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.


Related issues

Related to Ruby master - Feature #8246: Hash#traverseClosedmatz (Yukihiro Matsumoto)04/11/2013Actions
Related to Ruby master - Feature #8191: Short-hand syntax for duck-typingClosedmatz (Yukihiro Matsumoto)Actions
Related to Ruby master - Feature #11537: Introduce "Safe navigation operator"Closedmatz (Yukihiro Matsumoto)Actions

Also available in: Atom PDF