iOS Facebook 的 completionHandler 块有问题

Question

FBSDKGraphRequest *request = [[FBSDKGraphRequest alloc] initWithGraphPath:@"/me/friendlists" 
                                                               parameters:@{ @"fields": @"name",} 
                                                               HTTPMethod:@"GET"];
[request startWithCompletionHandler:^(FBSDKGraphRequestConnection *connection, id result, NSError *error) {
    if (!error)
        jsonArr1 = [result objectForKey:@"data"];

        //Inside the block
        for(int i=0; i<5; ++i)
            NSLog(@"%@", [[jsonArr1 objectAtIndex:i]objectForKey:@"name"]); //works fine
}]

//Outside the block
for(int i=0; i<5; ++i)
    NSLog(@"%@", [[jsonArr1 objectAtIndex:i]objectForKey:@"name"]); //gives out (null)

我发现块是异步调用的，这意味着仅在执行外部 for 循环后才调用块，这就是为什么它在块外给出 null 而在块内输出正常。

是否有任何解决方法可以在块外使用 jsonArr1？我想在 UITableView 的 tableView:cellForRowAtIndexPath 方法中使用该数组。

有人可以帮忙吗？ iOS.

网上没有最新的Fb整合教程

Answer 1

异步执行的全部要点是你调用一个带有完成处理程序的方法，方法 returns 立即安排真正的工作在其他队列而不是被调用的队列上完成，并且一旦方法的工作完成并且结果已准备好供您处理，回调处理程序将被调用。

因此，在您的完成处理程序中处理数据。如果您需要更新 UI，请执行以下操作：

[someFaceThingy doSomethingHere:@"/path/user/bobdobbs" completionHandler:^(NSDictionary *results, NSError *error ){
    if (!results) { .... process error and return ....}
    ... process results ...
    dispatch_async(dispatch_get_main_queue(), ^{
        ... apply results to table view ...
    });
}];

... don't process anything here because there'll be nothing to process ...

Answer 2

    Is this correct?
    I did the way just you said but still it isn't working out!

     -(void) viewDidLoad
    {
    [request startWithCompletionHandler:^(FBSDKGraphRequestConnection *connection, id result, NSError *error) {

    dispatch_queue_t aQueue = dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0);

    dispatch_async(aQueue, ^{ 
    jsonArr = [result objectForKey:@"data"];
    for(int i=0; i<[jsonArr  count]; ++i)
    {
    [ultimateArr addObject:[[jsonArr objectAtIndex:i]objectForKey:@"name"]]; 
         //Don't know why but objects are not being added to the ultimateArr

    NSLog(@"%@", [[jsonArr objectAtIndex:i]objectForKey:@"name"]);
}
dispatch_async(dispatch_get_main_queue(), ^{
[myTableView reloadData];
                        });

                });

            }];

        }

iOS Facebook 的 completionHandler 块有问题

Trouble with iOS Facebook's completionHandler block

objective-c

facebook-graph-api

ios

objective-c-blocks