Question

I’m really confused about using proprieties.
if i declare this

@property (nonatomic, strong) NSString* aString;

what is the difference between this

1.@synthesize aString = _aString

and

2.@synthesize aString;

if i want to use it, what is the difference between:

3. anOtherString = aString;

and

4. anOtherString = self.aString;

and

5. anOtherString = _aString;

I know that the _aString is the ivar, but the problem is the combination between 1,2,3,4,5.

for example, if i use 2 and 4, i’m i passing a reference to anOtherString or a copy of it ?
I usually use 2 and 4 is that the best choice for passing a reference ?

Answer 1

Your answer are here :

1.@synthesize aString = _aString

Ans: Your property name is aString but you are making an alias _aString. Now you can access aString, your accessors can be used by _aString only. From Xcode4.4 onwards this statement comes by default.

2.@synthesize aString;

Ans: This is the basic style of Objective-c synthesizing a property. From Xcode4.4 onwards this statement overrides the above one.

3.anOtherString = aString;

You are accessing the property by the reference variable/alias.

4.anOtherString = self.aString;

You are using accessor to get its value.

5.anOtherString = _aString;

You are accessing the property itself.

I usually use 2 and 4 is that the best choice for passing a reference ?

Ans : This is good way to do, as self. makes your class KVC compliant.