Ruby 2.7 new feature: Method reference operator

Seiei Miyagi on January 05, 2019

Method reference operator New operator .: was added. [Read Full]
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I really believe Ruby is moving in the wrong direction. This is not readable.


That's my example's problem.

Many other real world use-cases are on the issues.

It's handy in block argument for Enumerable methods like map, or select.


At first glance this seems a bit voodoo magic compared with the more explicit method, but the more I look at it, the more it does seem to be intuitive compared with other places : is used as a prefix in similar ways in Ruby.

Nice little upcoming addition.


: is used as a prefix in similar ways in Ruby.

Eh? : is never used as a prefix in Ruby. :: is—for namespacing in FQ names—but this is probably not as similar.

: as a prefix is used in Ruby only to declare symbols. If you think about [42].map(&:to_s) notation, there is no syntactic sugar. :to_s there is an old good plain symbol. It works because Symbol#to_proc is defined, no magic involved. & in arguments list calls to_proc on the argument and passes the result as a block to the calling method, e.g. symbol converted to a proc is passed to the receiver as a block parameter.

The naïve implementation of Symbol#to_proc in Ruby might be similar to the working implementation of the same for the string:

class String
  def to_proc
    ->(recv) { recv.send self }

#⇒ ["42"]

I don't like this syntax, at all.

It shaves off a few characters, but massively damages readability.

How is a new developer to make sense of this syntax? One thing ruby is really good at is "reading like English"; but this syntax appears more optimised for code golf than for human understanding.


In other programming languages, they have more convenient way to reference the method.

IMO, the difference between Ruby and other languages is method calling.
Other languages can reference the method by .method_name without (), but ruby can't because Ruby doesn't need () for method call.

The .: looks like method calling ., with additional : can reference the method. That makes sense to me.


With this syntactic sugar '"Enjoy!")' looks quite inconsistent :) Should be probably:


Updated the code, Thanks for improvements!

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