Question

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Difference between self.ivar and ivar?

I wonder, if I define an instance variable as property in Obj-C, for example,

@property (copy) NSString *str; 

and

@synthesize str = _str; 

should I access it within the instance methods by

_str = @"ABC";

or should I use the accessor, that is

[self setStr:@"ABC"];

Is there any general guideline regarding this?

Thanks very much!

Answer 1

It’s okay to read the instance variable from inside the class:

NSLog(@"str = %@", _str);

But don’t set the instance variable directly:

_str = @"ABC"; // No!

This bypasses the copy mechanism you’ve so carefully placed on your property. So do it this way instead:

[self setStr:@"ABC"]; // Ok
self.str = @"ABC";    // Ok, shorter