Question

My question maybe is silly but i cannot understand this. I create a singleton class using this code.

+ (GameRequestHandler *) sharedInstance
{
    static dispatch_once_t pred;
    static GameRequestHandler *shared = nil;

    dispatch_once(&pred, ^{
        shared = [[GameRequestHandler alloc] init];
    });
    return shared;
}

When i call methods from this singleton object, are they called on the main thread or in a background thread?

Answer 1

The methods are called on the thread you invoke them from.

dispatch_once just ensures that the block passed to it is only executed once in the lifetime of the application. I don’t think it uses threads and if it does, that is an implementation detail you don’t need to worry about.