while (!_dataArray) {
[NSTimer scheduledTimerWithTimeInterval:1 target:nil selector:nil userInfo:nil repeats:NO];
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
[NSTimer scheduledTimerWithTimeInterval:1 target:nil selector:nil userInfo:nil repeats:NO];
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
_dataArray中存的是网络返回的有效数据