objective-c - 等待代码执行完毕

Question

我想知道在 Objective C 项目中等待代码完成执行的最简单方法，因为我正在调用 Web 服务并检索结果，而是在 Web 服务完成调用和填充之前检索结果。

有什么建议吗？

顺便说一句，这是我的网络服务代码:

    NSMutableURLRequest *theRequest=[NSMutableURLRequest requestWithURL:tmpURl];

[theRequest addValue:@"text/xml; charset=utf-8" forHTTPHeaderField:@"Content-Type"];

[theRequest addValue:@"http://tempuri.org/GetCategory" forHTTPHeaderField:@"SOAPAction"];

NSString *msgLength=[NSString stringWithFormat:@"%i",[soapMessage length]];

[theRequest addValue:msgLength forHTTPHeaderField:@"Content-Length"];

[theRequest setHTTPMethod:@"POST"];

[theRequest setHTTPBody:[soapMessage dataUsingEncoding:NSUTF8StringEncoding]];

NSURLConnection *conn=[[NSURLConnection alloc] initWithRequest:theRequest delegate:self];

以及我用来从其他类调用此方法的代码:

images = [ws callWebService:api :data];

        images = [ws returnArray];

现在的问题是，第二行在第一行完成之前就被执行了

Answer 1

你很容易做到，如下所示，

-(void)aFunc {

Do Asynchronous A job...

while (A is not finished) {
// If A job is finished, a flag should be set. and the flag can be a exit condition of this while loop

// This executes another run loop.
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];

}

Do things using the A's result.

}