Question

I defined two classes: Player and HelloWorldLayer. In HelloWorldLayer, I defined a member variable: NSArray *bullets. In Player, I defined a member variable HelloWorldLayer *hwLayer. Now in one of Player‘s function, I want to visit bullets with hwLayer.bullets, but it doesn’t work and gives a compile error. I’ve attached screen shots – can anyone help me determine what’s wrong?

Answer 1

You forward-declare HelloWorldLayer in the header

@class HelloWorldLayer;

It lets you declare _hwlayer instance variable. However, it is not sufficient to start using its properties: but you must import the header that contains HelloWorldLayer into the .m file that references bullets.

Alternatively, you can use the square bracket syntax, like this:

[_hwlayer bullets]

This does not require importing the header.