custom class initializers with ARC - self.name or name? - objective-c

Question

when defining a Person class with ARC,
should i use self.fullname or just fullname in the initializer?
if i use fullname will the passed strings be retained?
if i use self.fullname i must define a setter or a property? should i use strong?
coming from a pre ARC way of thinking, i'm trying to wrap my head around the changes ARC suggests.

Answer 1

With ARC, these behave the same way, except that self.fullname will pass through the setter. The default setter will give you KVO-compliance. But otherwise, there is no difference.
Yes they will, if the pointers have been declared strong.
To use self.fullname = ... you must define a setter. For NSStrings and other classes which have mutable variants, it is usually recommended to use (copy).

Answer 2

In initializers, I'd advise against invoking any methods on self, because the object is in that unusual state where it lacks self-consistency. For the simple example you give, it doesn't make a difference right away. But if you later define your own -setFullname: method that reads or writes any other part of your object, invoking self.fullname = from your initializer will cause problems because the object isn't fully-formed yet.

Answer 3

I think the available answers need some clarification.
The long answer to your question
Look at this header:
Person : NSObject {
NSString *name; // better to call this _name to not confuse it with the property
// and even more better to not use an ivar, but only a property
}
#property (strong) NSString *name;
You have an instance variable. Usually you'd call your ivar the same as the property with an underscore, but often you'll find the ivar and the property have the same name.
It is also possible to only declare a property, in this case, the compiler will automatically insert an ivar with an underscore for you!
Now it is important to understand, that there is one major difference between name = #"John Smith" and self.name = #"John Smith", the first one directly sets the instance variable (aka _name = #"John Smith", disregarding memory management and (without ARC) creating a leak if the former value was not nil. Using the self-dot-syntax (self.name) uses the automatically generated accessor (=setter method), which respects the chosen memory management (typically retain or strong or copy).
Before properties and before ARC an object setter would have looked like this:
-(void)setName:(NSString*)newName {
if(newName != name) {
[name release];
name = newName;
[newName retain];
}
}
that means, the old iVar value is released and the new iVar value retained. All balanced and fine.
Now, with ARC and synthesized accessors (properties), you do not have to care about all this. While Properties synthesize acessors, ARC synthesizes and balanced retain/release calls based on an analysis of your code. So ARC and properties are not necessarily requiring each other, because they synthesize different aspects (note for example the different syntax "__weak" at the ivar declaration and "(weak)" at the property declaration?). But it's useful to know how it used to work, because now you'll see that there is a major difference between
name = #"John Smith"; // directly access ivar, the old value is never released
// your program is leaking if you're not using ARC
and going through the synthesized accessor
self.name = #"John Smith"; // old ivar released, new ivar set, all okay
The short answer to your question
do not use an ivar and a property if there is no need for both
self.property = newValue sets the new value by its setter method
ivar = newValue sets the new value directly, bypassing any setter method
it is definitely recommended to use the accessors and to not set ivars directly if there is a setter method (in other words: if you have a property, use its setter by calling self.property = newValue)