Question

working on xcode I realized that if I create a non-void method, I call it from a class / method, the result is processed optimally only if the action is immediate. I tried to do a test by inserting a delay and I realized that it no longer works.
I will write down here the example that I created:

Class A

//--------------------CLASS A
- (void)viewDidLoad {
   [super viewDidLoad];
   i = 0;
   Class *classB = [[Class alloc] init];
   i = [classB method1];
   [self performSelector:@selector(method3) withObject:NULL afterDelay:1.8];
}

-(void)method3 {
   NSLog(@"i = %i",i); // i = 0
}

Class B

//--------------------CLASS B    
-(int)method1 {
  [self performSelector:@selector(method2) withObject:NULL afterDelay:1];
  return a;
}

-(void)method2 {
  a = 800;
}

Obviously my problem is not something so trivial but I tried to make it easy to get an answer as thoroughly as possible, I was advised to use modal methods but I don’t think that’s the solution I was looking for.

What could I do to solve this?!

Answer 1

What you really need is a better understanding of asynchronous methods. In your method1, the variable a is never altered — all you are doing is scheduling method2 to be called in the future and then returning the current state of variable a.

In Objective-C, there are a few different ways you can solve this problem. People most commonly use protocols and delegates to solve this issue. Here is a basic intro to protocols and delegates. Basically, you would want your class A object to be a delegate of your class B object. You could also use NSNotifications or blocks, although you should probably understand the usage of protocols and delegates (they are very important in Objective-C) before moving on to notifications and blocks.