如何以編程方式在iOS中添加SubView？

Question

最初，我創建了一個名為MainView的視圖。在該視圖中，我放置了一個名為UnitsView的視圖。我的問題是：如果我想在MainView上添加UnitsView，則意味着必須使用self.view還是MainView。

UIView *MainView = [[UIViewalloc]initwithframe: CGRectMake    (0,0,self.view.frame.size.width, self.view.frame.size.height) ];
TopView.backgroundColor = [UIColor grayColor];
[self.view addSubview:TopView];

UIView *UnitsView = [[UIView alloc]init];
[self.view (or)MainView addsubView:UnitsView];

Answer 1

UIView *UnitsView = [[UIView alloc]initwithframe: CGRectMake(0,0,width,height)];
[MainView addsubView:UnitsView];
[self.view addSubView:MainView];

Answer 2

要在視圖上方添加視圖：-

UIView *UnitsView = [[UIView alloc]initwithframe:CGRectMake(0,0,100,100)];
UnitsView.backgroundColor = [UIColor grayColor];
[self.view addSubView:UnitsView];


UIView *SubUnit = [[UIView alloc]initwithframe:CGRectMake(0,0,50,50)];
SubUnit.backgroundColor = [UIColor greenColor];
[self.UnitsView addSubView:SubUnit];