Daniel Lee Daniel Lee - 1 year ago 72
Objective-C Question

Why does an NSInteger variable have to be cast to long when used as a format argument?

NSInteger myInt = 1804809223;
NSLog(@"%i", myInt); <====

The code above produces an error:

Values of type "NSInteger" should not be used as format arguments: add an explicit cast to 'long' instead.

The correct
message is actually
NSLog(@"%lg", (long) myInt);
Why do I have to convert the integer value of myInt to long if I want the value to display?


You get this warning if you compile on OS X (64-bit), because on that platform NSInteger is defined as long and is a 64-bit integer. The %i format, on the other hand, is for int, which is 32-bit. So the format and the actual parameter do not match in size.

Since NSInteger is 32-bit or 64-bit, depending on the platform, the compiler recommends to add a cast to long generally.

Update: Since iOS 7 supports 64-bit now as well, you can get the same warning when compiling for iOS.