Why isn't my variable being assigned

Question

Ok I think my understanding of properties in objective c may not be what I thought it was.

In my program I have a singleton that contains my class.

In my class during the init I assign a value from the singleton to my property.

I then assign a value to a property of that property.

However it does not keep the value and when I do a compare of the value in the singleton nothing has changed. What is going on here? Any ideas?

@interface MainGameLoop : NSObject {
    MapData *mapData;
}

@property (retain) MapData *mapData;

-(id) init
{
    self = [super init];
    GlobalVariables *sharedManager = [GlobalVariables sharedManager];
    self.mapData = sharedManager.mapData;   
    return self;
}

In a function of my class:

works:

sharedManager.mapData.currentPlayer = newCurrentPlayer;

does nothing:

self.mapData.currentPlayer == newCurrentPlayer;

Answer 1

self.mapData.currentPlayer == newCurrentPlayer;

Are you sure that you want two equal signs there? That statement is syntactically correct and will evaluate to either true or false.

Answer 2

== is a Boolean operator, while = is an assignment operator. Like what Dave said, if you are using an if statement such as if (self.mapData.currentPlayer == newCurrentPlayer) {…}, you would want to use == because it would evaluate to true or false, while = would be used to set the value of a variable, which is what I think you are trying to do.

If it's any consolation, I've made that mistake too many times to count…

Something that I do is to use NSLog() or printf() to make sure that each step is working correctly.