Singleton

h file

@interface LayerManager : NSObject
+ (id)sharedManager;

m file

@implementation Singleton
+ (id)sharedManager {
    static Singleton *sharedMyManager = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        sharedMyManager = [[self alloc] init];
    });
    return sharedMyManager;
}

- (id)init {
    if (self = [super init]) {
	//inital value of prop
	}
    return self
}