Question

Generally speaking, when should you make a variable in Objective C an instance variable?

For instance, say I got an UIViewController with an UILabel. In what cases would I have the UILabel as an instance variable vs doing something like this:

UILabel *label = [[UILabel alloc] init];
//set text of label
[view.addSubview label];
[label release];

Answer 1

In your particular example, the object is written as a variable so that it can be sent a release message after adding it to a view (which retains it).

The equivalent code without a variable is:

[view addSubview:[[[UILabel alloc] init] autorelease]];

We don’t need to send a release, because we’re autoreleasing the object.