为什么我不能在 GCD 中访问这个对象

Question

Server* mImpl;


void receiveImage()
{
    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        dispatch_async(dispatch_get_main_queue(), ^{
            [mImpl function];
        });
        return;
}

I have this peice of code above. For some reason, whenever this code is wrapped in a GCD as such, I get an error saying an -[UIWindowLayer function]: unrecognized selector sent to instance

Answer 1

The error message gives you your answer.

The problem is that " mImpl is defined as a UIWindowLayer and there is no such thing as " function " on a UIWindowLayer object.

And in fact, I don't even thing UIWindowLayer is a public Apple / iOS framework thing. You probably need to figure out why your " Server " is being declared in that function to be a UIWindowLayer. Did you define or set it up properly before " receiveImage " gets called?