AFJSONRequestOperation，如果操作成功则更新 UI

Question

我使用 AFNetworking 将数据发送到删除网络服务，具有以下块：

self.operation = [AFJSONRequestOperation JSONRequestOperationWithRequest:request success:^(NSURLRequest *request, NSHTTPURLResponse *response, id JSON) {

    [self updateAfterPost];


} failure:^(NSURLRequest *request, NSHTTPURLResponse *response, NSError *error, id jsonObject) {
    [handle error]
}];

- (void)updateAfterPost
{
    if ([AppController sharedAppController].currentUser.twitterAccount.crossPost.boolValue == YES) {
        [self postToTwitter];
    }
    [other things that should update the UI]
}

- (void)postToTwitter
{
    ACAccountType *accountType = [self.accountStore accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierTwitter];
    [self.accountStore requestAccessToAccountsWithType:accountType options:nil completion:^(BOOL granted, NSError *error) {
        if (granted == YES) {            
            if ([self.twitterAccounts count] > 0) {
                ACAccount *twitterAccount = [self.twitterAccounts objectAtIndex:[AppController sharedAppController].currentUser.twitterAccount.accountId.integerValue];
                NSDictionary *message = @{@"status":self.postTextField.text};
                NSURL *requestURL = [NSURL URLWithString:@"http://api.twitter.com/1/statuses/update.json"];
                SLRequest *postRequest = [SLRequest requestForServiceType:SLServiceTypeTwitter requestMethod:SLRequestMethodPOST URL:requestURL parameters:message];
                postRequest.account = twitterAccount;
                [postRequest performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error) {
                 }];
            }
        }
    }];
}

postToTwitter 操作会导致以下警告（如果我取消注释该方法，则不会发出警告）：

Obtaining the web lock from a thread other than the main thread or the web thread. UIKit   should not be called from a secondary thread.

我不知道如何解决它。我在成功块中尝试了NSNotification，但没有运气（通知也可能在后台线程中发送）。有什么想法或建议吗？

更新 我也试过[self performSelectorOnMainThread:@selector(updateAfterPost) withObject:nil waitUntilDone:YES];。

Answer 1

requestAccessToAccountsWithType 的完成块在任意队列上调用，因此您不能在其中调用 UI 元素（您的 postTextField）。

您应该使用 dispatch_async 调用来包装代码：

- (void)postToTwitter
{
    ACAccountType *accountType = [self.accountStore accountTypeWithAccountTypeIdentifier:ACAccountTypeIdentifierTwitter];
    [self.accountStore requestAccessToAccountsWithType:accountType options:nil completion:^(BOOL granted, NSError *error) {
        dispatch_async(dispatch_get_main_queue(), ^{
        if (granted == YES) {            
            if ([self.twitterAccounts count] > 0) {
                ACAccount *twitterAccount = [self.twitterAccounts objectAtIndex:[AppController sharedAppController].currentUser.twitterAccount.accountId.integerValue];
                NSDictionary *message = @{@"status":self.postTextField.text};
                NSURL *requestURL = [NSURL URLWithString:@"http://api.twitter.com/1/statuses/update.json"];
                SLRequest *postRequest = [SLRequest requestForServiceType:SLServiceTypeTwitter requestMethod:SLRequestMethodPOST URL:requestURL parameters:message];
                postRequest.account = twitterAccount;
                [postRequest performRequestWithHandler:^(NSData *responseData, NSHTTPURLResponse *urlResponse, NSError *error) {
                 }];
            }
        }
        });  
    }];
}