Is there any difference to use getters of sythesize properties or direct access to object? [duplicate]

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Possible Duplicate:

iVar property, access via self?

I understand that it's to use setters for instance variables, but are ther any reasons to use getters istead of direct access?

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NSArray *instArray;
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@property (nonatomic, retain)NSArray *instArray;
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@synthesize instArray;
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//are the following lines equal?
NSArray *array = [NSArray arrayWithArray:self.instArray];

NSArray *array = [NSArray arrayWithArray:instArray];

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For purely synthesized getters, there is no difference, unless you want atomic access (atomic properties surround the code with a lock).

For properties that have getters with extra code, there is a difference. Sometimes, it makes sense to avoid the extra code, so you use the ivar (say, xyz) directly. Otherwise,if you want the extra code to be invoked, you use the property, using self.xyz.