在Web服务呼叫响应中自动填写文本

将您的UITextField委托设置为您正在使用viewDidLoad:方法的ViewController

textField.delegate = self;

覆盖UITextField委托方法textField:shouldChangeCharactersInRange:replacementString: with：

- (BOOL)textField:(UITextField *)textField shouldChangeCharactersInRange:(NSRange)range replacementString:(NSString *)string{

    // To increase performance I advise you to only make the http request on a string bigger than 3,4 chars, and only invoke it
    if( textField.text.length + string.length - range.length > 3) // lets say 3 chars mininum
    {
        // call an asynchronous HTTP request
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{

            NSURL * url = [[NSURL alloc] initWithString:[NSString stringWithFormat:@"http:/example.com/search?q=%@", textField.text]];
            NSData * results = [NSData dataWithContentsOfURL:url];
            NSArray * parsedResults = [NSJSONSerialization JSONObjectWithData: results options: NSJSONReadingMutableContainers error: nil];
           // TODO: with this NSData, you can parse your values - XML/JSON
           dispatch_sync(dispatch_get_main_queue(), ^{
               // TODO: And update your UI on the main thread
               // let's say you update an array with the results and reload your UITableView
               self.resultsArrayForTable = parsedResults;
               [tableView reloadData];
           });
        });

    }

    return YES; // this is the default return, means "Yes, you can append that char that you are writing
    // you can limit the field size here by returning NO when a limit is reached
}