Mac开发，NSMenu、NSMenuItem的简单使用

在想要显示菜单的视图文件中添加如下代码：
-(void)rightMouseDown:(NSEvent *)event{    //创建Menu    NSMenu *theMenu = [[NSMenualloc] initWithTitle:@"Contextual Menu"];    //自定义的NSMenuItem    NSMenuItem *item3 = [[NSMenuItemalloc]init];    self.customView.wantsLayer =YES;    self.customView.layer.backgroundColor = [NSColorredColor].CGColor;    item3.title = @"Item 3";    item3.view = self.customView;    item3.target = self;    item3.action = @selector(beep:);        [theMenu insertItemWithTitle:@"Item 1"action:@selector(beep:)keyEquivalent:@""atIndex:0];    [theMenu insertItemWithTitle:@"Item 2"action:@selector(beep:)keyEquivalent:@""atIndex:1];    [theMenu insertItem:item3 atIndex:2];        [NSMenu popUpContextMenu:theMenuwithEvent:event forView:self.view];}-(void)beep:(NSMenuItem *)menuItem{    NSLog(@"_____%@", menuItem);}
- (void)setRepresentedObject:(id)representedObject {    [super setRepresentedObject:representedObject];
    // Update the view, if already loaded.}