Is there a difference between setting a property with the dot or the bracket syntax?

问题

Given the property declaration below, does method (A) work in exactly the same way as method (B)? I just want to check that self.yellowViewController = yellcon_New; is going via my setter, so that the old objects gets released and the new one retained.

// INTERFACE
@property(nonatomic, retain) YellowViewController *yellowViewController;

// IMPLEMENTATION (A)
self.yellowViewController = yellcon_New;

// IMPLEMENTATION (B)
[self setYellowViewController:yellcon_New];

回答1:

All of this is correct :

self.yellowViewController = yellcon_New;

And

[self setYellowViewController:yellcon_New];

Work the same. I would like to add something interesting : when you use

yellowViewController = yellcon_New;

you associate directly the value to the ivar, without going through your setter methode.

So if you have

-(void)setYellowViewController:(YellowViewController*)theYellowViewController;
{
    NSLog(@"Setting the yellow view controller");
    [yourWife askFor:beer];
    ...whatever...
    ...set the yellowViewController (retain in your case)
}

Calling

self.yellowViewController = yellcon_New;

and

[self setYellowViewController:yellcon_New];

will use the setter method (and log the message, and make your wife bring you some beer)

but

yellowViewController = yellcon_New;

will not.

It's interesting to know this in some cases.

回答2:

Yes, A and B lines work the same

You can check that by using @dynamic instead of @synthesize for this property and put NSLog message in you implementation of setter method.

回答3:

Yes. If you're using the @synthesize thing for that property, it's creating a -setYellowViewController: method for you.

来源：https://stackoverflow.com/questions/2207810/is-there-a-difference-between-setting-a-property-with-the-dot-or-the-bracket-syn