Interface type cannot be statically allocated?

Question

I tried to put this in the header file of my view object:

@property (nonatomic) UIColor color;

to store the color that lines should be draw

Answer 1

You need to declare a UIColor pointer like so and add retain/strong depending on whether you're using ARC or MRR:

@property (nonatomic, strong) UIColor *color;

Answer 2

The problem is that you can only access Objective-C objects by reference through pointers, like this:

UIColor *color;

you can't have a "bare" object, like this:

UIColor color;

So the solution is to insert the asterisk in your code (which you probably meant to do, and the bug is just a typo).

Answer 3

Your variable is for an object type, and as such must be declared as a pointer:

@property (nonatomic) UIColor * color;    // Note the asterisk

"Statically allocated" in this case would mean that the memory for that object was allocated at compile-time. All objects in Obj-C, however, are allocated at runtime and accessed through pointers.

"Interface type" is kind of an overly-technical term that's meaningful to the compiler, and not terribly important here. It means that UIColor represents the interface through which the compiler expects you to interact with the variable color. The actual type of the object pointed to may be different (as with a class cluster like NSString).