When is id promoted to instancetype?

instancetype is a special type that can be returned from an Objective-C method. It specifies that the return is an object of the same type as the receiving class. In some cases, the compiler promotes an id return to an instancetype: For instance, despite the definition of [[NSString alloc] init], the compiler knows that it […]

Objective-C property proposal: mainthreadonly

I’d like to propose a new language feature for Objective-C, a property attribute that would indicate that a property should only be set from the main thread. Let me be clear: Objective-C does not do this. But wouldn’t it be cool if it did?


Apple has a sample code package called Reachability. It wraps an iOS framework called SystemConfiguration, and can be used to determine network status, and catch events about networking going up and down. In the past, it’s been an ugly chunk of sample code, but it’s pretty respectable now. One thing Reachability is not, however, is […]