iOS 使用回调

Question

请原谅我的英语，我是法国人。

所以，我是 iOS 开发的新手。我开发了一种必须在异步任务后调用回调函数的方法。我搜索了选择器，但我真的不明白它是如何工作的......

这是我的代码:

NSString *const BaseURLString = @"http://mywebsite.fr/";
+ (void) getAdverts:(SEL *)myselector {
// 1
NSURL *baseURL = [NSURL URLWithString:[NSString stringWithFormat:BaseURLString]];

// 2
AFHTTPClient *client = [[AFHTTPClient alloc] initWithBaseURL:baseURL];
[client registerHTTPOperationClass:[AFJSONRequestOperation class]];
[client setDefaultHeader:@"Accept" value:@"application/json"];
[client getPath:@"jsoncall"
     parameters:nil
        success:^(AFHTTPRequestOperation *operation, id responseObject) {
            NSDictionary *jsonDict = (NSDictionary *) responseObject;
            NSArray *adverts = [jsonDict objectForKey:@"Advert"];

            NSMutableArray *advertList = [[NSMutableArray alloc] init];
            Advert *advert = [[Advert alloc] init];

            [adverts enumerateObjectsUsingBlock:^(id obj ,NSUInteger idx, BOOL *stop){
                advert.identifier = [(NSNumber *)[obj objectForKey:@"id"] integerValue];
                advert.title = [obj objectForKey:@"title"];
                advert.size = [obj objectForKey:@"size"];
                NSLog(@"ID:%d Size:%@", advert.identifier, advert.size);
                [advertList addObject:advert];
            }];

             // Use selector to callback a function
            [self performSelector:myselector withObject:@"test"];
        }
        failure:^(AFHTTPRequestOperation *operation, NSError *error) {
            UIAlertView *av = [[UIAlertView alloc] initWithTitle:@"Error Retrieving Weather"
                                                         message:[NSString stringWithFormat:@"%@",error]
                                                        delegate:nil
                                               cancelButtonTitle:@"OK" otherButtonTitles:nil];
            [av show];

        }
 ];
}

“调用者”代码:

- (void)viewDidLoad
{
    [super viewDidLoad];
    [ServerHelper getAdverts:@selector(mySelector)];
}

- (void)mySelector
{
    NSLog(@"selector ok");
}

错误在这里:发送到类的无法识别的选择器

非常感谢

Answer 1

您没有正确传递选择器，也没有正确调用它。

您不想传递指向 SEL 的指针，您只需要一个 SEL。方法应该是:

+ (void) getAdverts:(SEL)myselector {

但是，目前您有:

[self performSelector:myselector withObject:@"test"];

在此实例中，self 指的是定义了 getAdverts 类方法的类。不是已声明 mySelector 实例的类的实例。

如果你想这样做，你可能需要传入你希望调用选择器的对象。您的 getAdverts 方法需要类似于:

+ (void) getAdvertsWithTarget:(id)target selector:(SEL)myselector {

然后你会使用类似的东西回调:

[target performSelector:myselector];

并按如下方式调用它:

[ServerHelper getAdvertsWithTarget:self selector:@selector(mySelector)];