ios - 更新 block 内的 UI

Question

我调用 youtube API 来获取视频的标题。然后我想在表格中的屏幕上显示视频的标题。 block 执行完毕后，如何访问 title？

获取标题的代码如下

-(void)getVideoTitle:(NSString *)urlStr success:(void (^)(NSDictionary *responseDict))success{

urlStr = [NSString stringWithFormat:@"https://www.googleapis.com/youtube/v3/videos?part=contentDetails%%2C+snippet%%2C+statistics&id=%@&key={API_KEY}",urlStr];

NSURL *url = [[NSURL alloc] initWithString:urlStr];
// Create your request
NSURLRequest *request = [NSURLRequest requestWithURL:url];

// Send the request asynchronously
[[[NSURLSession sharedSession] dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *connectionError) {

    // Callback, parse the data and check for errors
    if (data && !connectionError) {
        NSError *jsonError;
        NSDictionary *jsonResult = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&jsonError];

        if (!jsonError) {
            success(jsonResult);
           // NSLog(@"Response from YouTube: %@", jsonResult);
        }
    }
}] resume];

下面是我如何调用上面的函数:

    [self getVideoTitle:@"zB4I68XVPzQ" success:^(NSDictionary *responseDict){
    NSArray *itemsArray = [responseDict valueForKey:@"items"];
    NSDictionary *item = itemsArray[0];
    NSDictionary* snippet = [item valueForKey:@"snippet"];
    NSString *title = [snippet valueForKey:@"title"];
}];

block 执行完毕后如何访问 block 外的title变量？

我尝试了以下但没有成功

    dispatch_async(dispatch_get_main_queue(), ^{
    [self updateMyUserInterfaceOrSomething];
});

Answer 1

在您的代码中:

    NSString* recievedTitle __block = nil; //title is here, after block below run

    [self getVideoTitle:@"zB4I68XVPzQ" success:^(NSDictionary *responseDict){
        NSArray *itemsArray = [responseDict valueForKey:@"items"];
        NSDictionary *item = itemsArray[0];
        NSDictionary* snippet = [item valueForKey:@"snippet"];
        recievedTitle = [snippet valueForKey:@"title"]; //here you write it
        // or
        NSString *title = [snippet valueForKey:@"title"];
        [self updateInterfaceWithTitle: title]
    }];

///

- (void)updateInterfaceWithTitle:(NSString*)title{
   //use title here
}