Autoconfiguring singleton objective-c class method

Generic Singleton

// Created by Adam Roberts on 13/10/2014 BSD License

// Place in .h file in @interface section
+(instancetype)sharedManager;

// Place in .m file in @implementation section
+(instancetype)sharedManager{
    
    static dispatch_once_t pred;
    static id sharedManager = nil;
    
    dispatch_once(&pred, ^{
        sharedManager = [[[self class] alloc] init];
    });
    return sharedManager;
}