Question

A requirement of A.B is that A must declare @synthesize before using the setter or getter
but A->B doesn’t require this.

I don’t understand which is better and what one uses the least amount of memory?

If I convert from A.B to A->B will it use less memory or the same amount?
A->B uses less memory because you don’t need to declare @synthesize, right?

Answer 1

If a is an Objective-C object then a.b = c; is the same as to write [a setB:c];.

setB: in this case is a default name for automatic generated setter method when you are specifying @property (...) typeB b; and @synthesize b. Instead of ... you can place corresponding memory specifier, as retain, assign, copy.
By writing a->b = c you avoid using setter method, and access b directly.

So, construction a->b generates less extra-code but breaks one of the major OOP notion of “Encapsulation” and you also should handle memory related staff manually.

For example if you’ve specified retain in b‘s @property, then construction a.b = c will behave almost in the same fashion as a->b = [c retain].