CODEWITHSUNDEEP
objective-c
DNB5brims
DNB5brims

Reputation: 30618

What is the different between the self.xxx and calling xxx directly in Obj-C?

For example, I have a UIViewController, and have a value:

NSString *testString;

@property (nonatomic, retain) NSString *testString;

in the .m:

@synthesize testString;

And what is the different between these two lines of code:

testString = @"something";
self.testString = @"something";

Upvotes: 0

Views: 358

Answers (3)

Mike K
Mike K

Reputation: 2227

in non-ARC code there is a significant difference if you're declaring properties as retain or copy. in these two cases, there's a bit more going on behind the scenes when you call self.property. very simplistically, retain does something like:

- (void)setFoo:(NSString *)newFoo {
  [newFoo retain];
  [foo release];
  foo = newFoo;
}

and with copy it'd be something like:

- (void)setFoo:(NSString *)newFoo {
  NSString *oldFoo = foo;
  foo = [newFoo copy];
  [oldFoo release];
}

}

Upvotes: 0

stefanB
stefanB

Reputation: 79870

The first case assigns new value to testString, you are accessing testString directly:

testString = @"something";

In the second case:

self.testString = @"something";

You are calling setter generated by calling @synthesize testString and the fact that it's a property.

The second case calls generated [aUIViewControllerObject setTestString: @"something"] in which the @"something" NSString is retained (because the testString property is declared with retain parameter), the old value is autoreleased or released and the new value is assigned to testString.

Upvotes: 1

brigadir
brigadir

Reputation: 6942

self.testString = @"something"; implicitly calls setTestString: method. In your case it means following:

-(void) setTestString: (NSString*) newString
{
    if (testString != newString)
    {
        [testString release];
        testString = [newString retain];
    }
}

Upvotes: 0

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