如何获取数据从NSURLSessionDataTask返回

我有一个注册视图控制器处理所有的用户input，并调用另一个类（wsClass）传递给它的函数，该数据作为NSDictionary。

wsClass中的函数被调用并build立连接，数据从服务器返回并在会话中可用。

我的问题是，如何返回数据到注册视图控制器，最初调用函数，它总是空的。

这是在registrationViewController中的调用：

wsClass *ws = [[wsClass alloc] init]; NSDictionary *testDict = [[NSDictionary alloc] initWithObjectsAndKeys:username.text,@"username",email.text,@"email",password.text,@"password", nil]; NSDictionary *respDict = [ws sendData:testDict]; 

这是在wsClass.m中调用的函数：

 - (NSDictionary *)sendData:(NSDictionary *)sendDict { NSMutableString *sendStr = [[NSMutableString alloc] init]; [sendDict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) { [sendStr appendFormat:@"&%@=%@", key, obj]; }]; NSLog(@"sendStr is: %@",sendStr); NSString *noteDataString = [NSString stringWithFormat:@"%@%@",REQUIRED,sendStr]; NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration]; NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfiguration]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:urlTest]]; request.HTTPBody = [noteDataString dataUsingEncoding:NSUTF8StringEncoding]; request.HTTPMethod = @"POST"; NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { // The server answers with an error because it doesn't receive the params // handle response if(error == nil) { [getReqAlert dismissWithClickedButtonIndex:0 animated:YES]; NSError *e = nil; jsonArray = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableLeaves error: &e]; if (!jsonArray) { NSLog(@"Error parsing JSON: %@", e); } else { NSLog(@"resp: %@ = %@",[jsonArray objectForKey:@"status"],[jsonArray objectForKey:@"msg"]); NSLog(@"Dictionary count: %lu", jsonArray.count); } } }]; [postDataTask resume]; return jsonArray; 

}

Answer 1

这个post是asynchronous完成的，所以你的wsClass需要在完成后告诉调用者完成。 一个很好的方法是使用由调用者提供的代码块来增加sendData方法，该代码块应该在完成时运行：

改变sendData:看起来像这样：

 // it doesn't return anything, because all it does is launch the post // but when the post is done, it invokes completion - (void)sendData:(NSDictionary *)sendDict completion:(void (^)(NSDictionary *))completion { // the stuff you're already doing NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { // the stuff you're already doing // now tell the caller that you're done completion(jsonArray); }]; } 

调用者现在看起来像这样：

 // change the UI to say "I'm busy doing the post" [ws sendData:testDict completion:^(NSDictionary *responseDict) { NSLog(@"this runs later, after the post completes %@", responseDict); // change the UI to say "The post is done" }]; 

关于这一点只是一些笔记：（1）我没有添加一个错误参数的块，你可能应该。 检查并调用块的nil和一个错误，或与json输出和error = nil。 （2）你的代码假定json结果parsing为字典。 确保在代码假设之前总是如此。 （3）class级名称通常以大写字母开头。

Answer 2

这可能工作。

1. 为NSDict添加一个接口variablesnsDictVariable，或者在类中检索的任何东西
2. 在SendData中分配它：self.nsDictVariable = ….

Answer 3

尝试这个 。 这将工作得很好。

 -(void)loadDetails { NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration]]; [[session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { _allVehicleLocationsArray = [NSJSONSerialization JSONObjectWithData:data options:0 error:nil]; [self afterCompleteDoThis]; }] resume]; } -(void)afterCompleteDoThis{ for (NSDictionary *vehicleDict in _allVehicleLocationsArray) { NSLog(@" PPP %@" , [vehicleDict valueForKey:@"vehicleType"]); } } 

Answer 4

您可以使用Semaphores进行wading，直到块完成执行，然后从函数返回值

 - (NSDictionary *)sendData:(NSDictionary *)sendDict { NSMutableString *sendStr = [[NSMutableString alloc] init]; [sendDict enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) { [sendStr appendFormat:@"&%@=%@", key, obj]; }]; NSLog(@"sendStr is: %@",sendStr); NSString *noteDataString = [NSString stringWithFormat:@"%@%@",REQUIRED,sendStr]; NSURLSessionConfiguration *sessionConfiguration = [NSURLSessionConfiguration defaultSessionConfiguration]; NSURLSession *session = [NSURLSession sessionWithConfiguration:sessionConfiguration]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:urlTest]]; request.HTTPBody = [noteDataString dataUsingEncoding:NSUTF8StringEncoding]; request.HTTPMethod = @"POST"; let semaphore = dispatch_semaphore_create(0) NSURLSessionDataTask *postDataTask = [session dataTaskWithRequest:request completionHandler:^(NSData *data, NSURLResponse *response, NSError *error) { // The server answers with an error because it doesn't receive the params // handle response if(error == nil) { [getReqAlert dismissWithClickedButtonIndex:0 animated:YES]; NSError *e = nil; jsonArray = [NSJSONSerialization JSONObjectWithData: data options: NSJSONReadingMutableLeaves error: &e]; if (!jsonArray) { NSLog(@"Error parsing JSON: %@", e); } else { NSLog(@"resp: %@ = %@",[jsonArray objectForKey:@"status"],[jsonArray objectForKey:@"msg"]); NSLog(@"Dictionary count: %lu", jsonArray.count); dispatch_semaphore_signal(semaphore) } } }]; [postDataTask resume]; dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER) return jsonArray; 

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