Ios Singleton不返回任何图像

我试图从FB获取配置文件图像，并使用singleton类保存它，但当我尝试在UIImageView中显示它时，它似乎没有保存任何图像。我已经测试了获取facebook个人资料图像的代码，它可以正常工作。为什么使用singleton不起作用

单子 单子 ViewController.h-保存UIImage AnotherViewController.m-获取表单单例类

---

在您的情况下，当您调用

[FBSingleton sharedInstance]

时，将不会调用

FBSingleton

类的

init

方法，因为在

+sharedInstance

中，您调用了

[super allocWithZone]

，而不是

[self new]即最终版本必须如下所示：

+ (instancetype)sharedInstance
{
    static id instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [self new]; //or [[self alloc] init] which is the same
    });

    return instance;
}

您在singleton类init中错过了
@synchronized（self）

FBSingleton *sharedInstance = nil;

// Get the shared instance and create it if necessary.

    + (FBSingleton *)sharedInstance {
        @synchronized(self){
            if (sharedInstance == nil) {
                sharedInstance = [[super allocWithZone:NULL] init];
            }
        }
        return sharedInstance;
    }

    UIImage *theImage = [[FBSingleton sharedInstance] userImage];

    if (!theImage) {
        // download the image from Facebook and then save it into the singleton



        [FBRequestConnection
         startForMeWithCompletionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
             if (!error) {
                 NSString *facebookId = [result objectForKey:@"id"];

             FBSingleton *sharedSingleton = [FBSingleton sharedInstance];

                UIImage *image = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:@"https://graph.facebook.com/%@/picture?type=large", facebookId ]]]];

                 sharedSingleton.userImage = image;

             }
         }];




    }

FBSingleton *sharedSingleton = [FBSingleton sharedInstance];
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(tableView.frame.size.width/2-75, 50.0f, 100.0f, 100.0f)];
    [imageView setImage:sharedSingleton.userImage];

    [self.view addSubview:imageView];

+ (instancetype)sharedInstance
{
    static id instance = nil;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        instance = [self new]; //or [[self alloc] init] which is the same
    });

    return instance;
}

FBSingleton *sharedInstance = nil;

// Get the shared instance and create it if necessary.

    + (FBSingleton *)sharedInstance {
        @synchronized(self){
            if (sharedInstance == nil) {
                sharedInstance = [[super allocWithZone:NULL] init];
            }
        }
        return sharedInstance;
    }