Feature #10883: Passing a block to itself

• Status: Open
• Priority: Normal
• Assignee: -
• Target version: -

[Gondolin (Damien Robert)]

In the discussion of itself
some people proposed that passing a block to itself could return the value of the block:

def itself
  if block_given?
    yield self
  else
    self
  end
end

It would be very usefull in method chains

#this would allow
an_array.foo.bar.itself {|x| x[1..x.length-1]}.baz
#which flows better than
a=an_array.foo.bar
a[1..a.length-1].baz

[phluid61 (Matthew Kerwin)]

Not exactly a duplicate, but also see the discussion at #6373

[recursive-madman (Recursive Madman)]

Note that for your example that wouldn't be needed:

a = an_array.foo.bar
a[1..a.length-1].baz

is equivalent to

an_array.foo.bar[1..-1].baz

[shan (Shannon Skipper)]

I think having a block form of #itself would be great. Here's a highly contrived example:

(("123".to_i - 3).to_s.reverse.to_i * 2).to_s
#=> "42"

Instead of nested parens, the following reads left to right:

"123".to_i.itself { |n| n - 3 }.to_s.reverse.to_i.itself { |n| n * 2 }.to_s
#=> "42"

It also allows a variety of other niceties:

["Hello", "Word"].itself { |greeting, subject| "#{greeting}... #{subject}!!" }
#=> "Hello... Word!!"

So like #tap except it returns itself instead of just tapping in.

[nobu (Nobuyoshi Nakada)]

Why itself doesn't return itself?
It seems very confusing.

[baweaver (Brandon Weaver)]

Nobuyoshi Nakada wrote:

Why itself doesn't return itself?
It seems very confusing.

Why can't we just tie into the current verbiage?

# Yes, contrived
1.yield { |v| v + 5 } # => 6

def defaults_to(default)
  -> v { v || default }
end

nil.yield(&defaults_to(5)).times do # ....

[avit (Andrew Vit)]

Duplicate of: #6373, #10095