我们都知道如何用 Objective-C 创建 NSAlert：
NSAlert *alert = [[[NSAlert alloc] init] autorelease];
[alert addButtonWithTitle:@"Delete"];
[alert addButtonWithTitle:@"Cancel"];
[alert setMessageText:@"Delete the document?"];
[alert setInformativeText:@"Are you sure you would like to delete the document?"];
[alert setAlertStyle:NSWarningAlertStyle];
[alert beginSheetModalForWindow:[self window] modalDelegate:self didEndSelector:@selector(alertDidEnd:returnCode:contextInfo:) contextInfo:nil];
假设 alert 用于确认用户是否想删除某个文档。
我们希望“删除”按钮运行删除函数，“取消”按钮只需隐藏 alert 即可。
但如何用 Swift 实现呢？
从 OS X 10.10 Yosemite 版本开始 beginSheetModalForWindow:modalDelegate 就已经被弃用了
func dialogOKCancel(question: String, text: String) -> Bool {
let myPopup: NSAlert = NSAlert()
myPopup.messageText = question
myPopup.informativeText = text
myPopup.alertStyle = NSAlertStyle.warning
myPopup.addButton(withTitle: "好的")
myPopup.addButton(withTitle: "取消")
return myPopup.runModal() == NSAlertFirstButtonReturn
}
let answer = dialogOKCancel(question: "确认？", text: "请选择。")
该方法根据用的选择返回 true 或 false。
NSAlertFirstButtonReturn 表示添加进 alert 的第一个按钮，这里就是“好的”。
