参考文章
虽然部分API已经停止使用，但是作者总结的还是相当详细的，值得一看。

* To display an informative message
* To take confirmation from user before continuing with a transaction
* As a success or failure response to the end user.
* Giving the user more than one option to take a action (save, dont-save, cancel etc).
* An NSAlert object displays an application model or as a sheet attached to a document window.

上代码

- (IBAction)showAlert:(NSButton *)sender {
    NSAlert * alert = [[NSAlert alloc]init];
    alert.messageText = @"This is messageText";
    alert.alertStyle = NSAlertStyleInformational;
    [alert addButtonWithTitle:@"continue"];
    [alert addButtonWithTitle:@"cancle"];
    [alert setInformativeText:@"NSWarningAlertStyle \r Do you want to continue with delete of selected records"];
    [alert beginSheetModalForWindow:[self.view window] completionHandler:^(NSModalResponse returnCode) {
        NSLog(@"xxx");
        if (returnCode == NSModalResponseOK){
            NSLog(@"(returnCode == NSOKButton)");
        }else if (returnCode == NSModalResponseCancel){
            NSLog(@"(returnCode == NSCancelButton)");
        }else if(returnCode == NSAlertFirstButtonReturn){
            NSLog(@"if (returnCode == NSAlertFirstButtonReturn)");
        }else if (returnCode == NSAlertSecondButtonReturn){
            NSLog(@"else if (returnCode == NSAlertSecondButtonReturn)");
        }else if (returnCode == NSAlertThirdButtonReturn){
            NSLog(@"else if (returnCode == NSAlertThirdButtonReturn)");
        }else{
            NSLog(@"All Other return code %ld",(long)returnCode);
        }
    }];
    
}

多个按钮的Alert

- (IBAction)showDifferentAlert:(NSButton *)sender {
    NSAlert * alert = [[NSAlert alloc]init];
    alert.messageText = @"This is messageText";
    alert.alertStyle = NSAlertStyleInformational;
    [alert addButtonWithTitle:@"Button One"]; //will generate a return code of 1000
    [alert addButtonWithTitle:@"Button Two"]; //will generate a return code of 1001
    [alert addButtonWithTitle:@"Button Three"]; //will generate a return code of 1002
    [alert addButtonWithTitle:@"Button Four"]; //will generate a return code of 1003
    [alert addButtonWithTitle:@"Button Five"]; //will generate a return code of 1004
    [alert setInformativeText:@"NSWarningAlertStyle \r Do you want to continue with delete of selected records"];
    [alert beginSheetModalForWindow:[self.view window] completionHandler:^(NSModalResponse returnCode) {
        if (returnCode == NSAlertFirstButtonReturn) {
            NSLog(@"(returnCode == NSAlertFirstButtonReturn)");
        }else if(returnCode == NSAlertSecondButtonReturn){
            NSLog(@"(returnCode == NSAlertSecondButtonReturn)");
        }else if(returnCode == NSAlertThirdButtonReturn){
            NSLog(@"(returnCode == NSAlertThirdButtonReturn)");
        }else if (returnCode == NSAlertThirdButtonReturn){
            NSLog(@"All Other return code %ld",(long)returnCode);
        }else{
            NSLog(@"All Other return code %ld",(long)returnCode);
        }
    }];
}

相对来说还是很简单的，相对UIAlertViewController还是很相似的。