Feature #7748

Contextual send

Added by Thomas Sawyer about 1 year ago. Updated 4 months ago.

[ruby-core:51719]
Status:Open
Priority:Normal
Assignee:Yukihiro Matsumoto
Category:core
Target version:Next Major

Description

=begin
If I write a method that uses #send vs. #public_send, I am making an assumption about how that method is invoked. For example, take the simplest form of such a method:

class String
def send_out(op, *a, &b)
send(op, *a, &b)
end
end

This code has a bug in it, in the sense that it can be used to call private string methods. The solution is to use #public_send. In most cases that will be fine. But if anyone tries to reuse the method while extending String themselves, e.g.

class String
def sendout(op, *a, &b)
public
send(op, *a, &b)
end

def some_public_method
  send_out(:some_private_method)
end

private
def some_private_method
end

end

Then it will be a problem b/c it cannot be used on a private supporting method.

So it seems like there should be something like a ((contextual send)) which invokes a send with the same visibility as the parent method is invoked. e.g.

class String
def sendout(op, *a, &b)
contextual
send(op, *a, &b)
end
end

And then all cases will work as expected.
=end

History

#1 Updated by Nobuyoshi Nakada about 1 year ago

#send had been implemented in that manner once, but reverted and #public_send was separated instead.

#2 Updated by Thomas Sawyer about 1 year ago

Ah, so this has been thought of before. I agree it should not replace behaviour of private #send (although, how much sweeter the syntax if it were called #private_send ?). But as an additional method, it would be useful.

Or was there some reason, other than zonking #send, that made it "bad"?

#3 Updated by Koichi Sasada about 1 year ago

  • Assignee set to Yukihiro Matsumoto

I think matz tried it.
Matz: Could you give us your knowledge?

#4 Updated by Yukihiro Matsumoto about 1 year ago

=begin
What I did was allowing ((%send%)) to invoke public method when called without explicit receiver.

And I gave up the idea because (a) it made send behavior more complex, (b) it slightly slowed down #send, (c) it was difficult to implement it in other implementations.

Matz.
=end

Also available in: Atom PDF