What does "Must explicitly describe intended ownership of an object array parameter" mean and how can I fix it?

Question

There is something wrong with the first line of the following function definition:

void draw(id shapes[], int count)
{   
    for(int i = 0;i < count;i++) {
        id shape = shapes[i];
        [shape draw];
    }
}   

Compilation fails with the error "Must explicitly describe intended ownership of an object array parameter".

What is the exact cause of the error? How can I fix it?

Answer 1

You are passing an array of pointers in an ARC environment. You need to specify one of the following:

• __strong
• __weak
• __unsafe_unretained
• __autoreleasing

I think in your case __unsafe_unretained should work, assuming that you do not do anything to the shapes that you pass to draw() concurrently.

void draw(__unsafe_unretained id shapes[], int count)
{
    for(int i = 0;i < count;i++) {
        id shape = shapes[i];
        [shape draw];
    }
}