Question

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";

Answer 1

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.