Feature #13807

A method to filter the receiver against some condition

Added by sawa (Tsuyoshi Sawada) 10 months ago. Updated 10 months ago.

Target version:


I frequently see code that uses some value if that value satisfies a certain condition, and something else otherwise.

a.some_condition ? a : b

And in most cases, the value of a is non-nil when the condition is satisfied.

I propose to have a method, perhaps named verify, which would implemented to be equivalent to this definition:

class Object
  def verify
    self if yield(self)

Then, we can write the expression above (assuming a is non-nil when the condition is satisfied) like this:

a.verify{|a| a.some_condition} || b

Perhaps it would also be useful to do something like:

a.verify{|a| a.some_condition}&.chaining_of_more_methods


#1 [ruby-core:82357] Updated by shevegen (Robert A. Heiler) 10 months ago

I have no particular pro or con opinion about your proposal, but I just
want to say that the last variant is not very pretty.

The lonely guy operator staring at the dot before him is pressed hard
against the wall behind him there, the "}" character!

#2 [ruby-core:82360] Updated by duerst (Martin Dürst) 10 months ago

I don't see any improvement. The new way that would be possible with the verify method is longer and more complicated than the simple and straightforward a.some_condition ? a : b.

#3 [ruby-core:82361] Updated by nobu (Nobuyoshi Nakada) 10 months ago

It seems useless without method chain, i.e., variable a is too simple as an example.

That is, this is a variant of yield_self. {|a| a.some_condition ? a : b}

or {|a| a.some_condition} || b || b

But verify is long and sounds ambiguous.

This came to my mind, but looks magical a little. || b

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