Question

Will doSomeCalculations be called if a is nil?


a.position = [self doSomeCalculations];


I guess it has to as doSomeCalculations can alter the state, but I’m not sure.

Answer 1

If position is a property and you rewrite the statement to the equivalent bracket syntax, you end up with:

[a setPosition:[self doSomeCalculations]];

No lazy evaluation is performed here. It’s not any different from nested function calls when you consider that all these bracketed expressions are transformed into function calls to objc_msgSend():

objc_msgSend(a, sel_getUid("setPosition:"), objc_msgSend(self, sel_getUid("doSomeCalculations")));

The bottom line is, [self doSomeCalulations] is evaluated even if a is nil.