OC 中单例的实现

sharedInstance

#import "RageIAPHelper.h"

@implementation RageIAPHelper

+ (RageIAPHelper *)sharedInstance {
    static dispatch_once_t once;
    static RageIAPHelper * sharedInstance;
    dispatch_once(&once, ^{
        NSSet * productIdentifiers = [NSSet setWithObjects:
                                      @"pw.xkk.inapprangewythest.nightlyrage",
                                      @"pw.xkk.inapprangewythest.drummerrage",
                                      @"pw.xkk.inapprangewythest.randomrageface",
                                      nil];
        sharedInstance = [[self alloc] initWithProductIdentifiers:productIdentifiers];
    });
    return sharedInstance;
}

@end