IOS弹出提示框

- (void)showAlertView:(NSString *)message{

    UIAlertView *alert = [[UIAlertView alloc] initWithTitle:@"" message:message delegate:self cancelButtonTitle:@"确定" otherButtonTitles:nil, nil];

    [alert show];

}

如果提示说：

This application is modifying the autolayout engine from a background thread, which can lead to engine corruption and weird crashes.  This will cause an exception in a future release.

那么使用的时候就切换到单一主线程里：

dispatch_async(dispatch_get_main_queue(), ^{

   [self showAlertView:@"登录失败"];

});