Why override on OneClass.new as following code not cause infinite loop?

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1 
class A
  def initialize
    puts "foo"
  end

  def self.new
    new.tap do |o|
      puts "bar"
      yield o
    end
  end
end

a = A.new
# => "foo"

a1 = A.new { |o| p o }
# => foo
# => bar
# => #<A:0x7fd9456aae60>

It’s seem like it only works when yield the new object to block, i guess the new object within the new method was tap into the block, something strange is happening, but i don’t understand why.

Thanks

2

Pretty sure it works since your normal initialize method creates a non-yielding new method. Since your custom .new method does yield, it first calls into the non-yielding variant, then goes into your #tap code which is why both foo and bar is printed.

3

The blockless and yielding overloads are separate in Crystal, unlike in Ruby. This is the main motivation behind making the formatter append a block parameter to the second overload automatically.

2 Likes
4

Actually, I knew override above, but the main reason I didn’t understand it before is that I didn’t realize that initialize creates a non-block version of new.

There is some cunning here.