objective-c - 将加载 gif 添加到 NSAlert

Question

我想在我的 NSAlert 中添加一个加载 gif 我已经尝试过了，但它似乎不起作用：

NSProgressIndicator * gif;
gif.style = NSProgressIndicatorSpinningStyle;
[gif startAnimation:self];

NSAlert *alert = [[NSAlert alloc] init];
[alert setInformativeText:@"Please check your internet connection and try again."];
[alert setMessageText:@"Connection Error"];
[alert setAlertStyle:NSWarningAlertStyle];
[alert setAccessoryView:gif];
[alert runModal];

任何想法我做错了什么？