Shared Controller

SharedController.h

+ (instancetype)sharedController;

SharedController.m

+ (instancetype)sharedController
{
    static <#Class#> *sharedInstance = nil;
    static dispatch_once_t pred;
    dispatch_once(&pred, ^{
        sharedInstance = [[<#Class#> alloc] init];
    });
    
    return sharedInstance;
}