[natesm]

Those first two and following aren't equivalent, are they? Wouldn't they compile, respectively, to:

    objc_msgSend(self, @selector(bar));

And:

    objc_msgSend(self, @selector(performSelector:), @selector(bar));

?

[Zev]

The first two are the same, with a different syntax, yes.

They would both become:

  objc_msgSend(self, @selector(bar));

However, your examples are basically explicitly passing a message (1 and 2), vs dynamically building a message to pass (3).

For the second to work, the objc_msgCall function would really be:

  objc_msgSend(self, @selector(performSelector:), @selector(bar));

(The first example is saying to self to call the selector (method) named 'bar'. The second example is telling self to call the method 'performSelector:' with an argument of 'bar'.)

The runtime may or may not be smart enough to optimize this out. It has never been a bottleneck for me to bother looking into it, and I haven't come across anything to indicate one way or the other.