使用闭包的小案例（一）传参和返回值

需求描述：

在控制器的view上创建一个scrollView,里面添加若干个button

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let sc = UIScrollView()
        sc.backgroundColor = UIColor.red
        let buttonW = 80
        let btnCount = 8
        for i in 0..<btnCount
        {
            let btn = UIButton()
            btn.backgroundColor = UIColor.green
            btn .setTitle("按钮\(i)", for: UIControlState.normal)
            btn.frame = CGRect(x:buttonW*Int(i), y:0, width:buttonW, height:44)
            sc.addSubview(btn)
        }
        sc.frame = CGRect(x:0, y:100, width:view.bounds.size.width, height: 44)
        sc.contentSize = CGSize(width:8*buttonW, height:44)
        view.addSubview(sc)
    }
}

需求描述：用函数实现上面需求，并且创建button个数使用闭包返回

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        let sc = creatSubViewsWithCount(buttonCount: { () -> (Int) in
            return 8
        })
        view.addSubview(sc)
    }

    func creatSubViewsWithCount(buttonCount:() -> (Int)) -> UIScrollView {
        let sc = UIScrollView()
        sc.backgroundColor = UIColor.red
        let buttonW = 80
        let btnCount = buttonCount()
        for i in 0..<btnCount
        {
            let btn = UIButton()
            btn.backgroundColor = UIColor.green
            btn .setTitle("按钮\(i)", for: UIControlState.normal)
            btn.frame = CGRect(x:buttonW*Int(i), y:0, width:buttonW, height:44)
            sc.addSubview(btn)
        }
        sc.frame = CGRect(x:0, y:100, width:view.bounds.size.width, height: 44)
        sc.contentSize = CGSize(width:8*buttonW, height:44)
        return sc
    }
}

需求描述：用函数实现上面需求，并且创建子控件个数使用闭包返回，子控件类型是什么，也由另一个闭包决定（即灵活性好，易扩展）

分析：
闭包1返回参数： 返回创建子控件的个数
闭包2传入参数：第几个子控件的索引
闭包2返回参数：第几个新创建的子控件

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        
        let sc = creatSubViewsWithCount(buttonCount: { () -> (Int) in
            return 8
        }, buttonWithCount: { (index) -> (UIButton) in
            let buttonW = 80
            let btn = UIButton()
            btn.backgroundColor = UIColor.green
            btn .setTitle("按钮\(index)", for: UIControlState.normal)
            btn.frame = CGRect(x:buttonW*Int(index), y:0, width:buttonW, height:44)
            return btn
        })
        view.addSubview(sc)
    }

    func creatSubViewsWithCount(buttonCount:() -> (Int),buttonWithCount:(Int) -> (UIButton)) -> UIScrollView {
        let sc = UIScrollView()
        sc.backgroundColor = UIColor.red
        let buttonW = 80
        let btnCount = buttonCount()
        for i in 0..<btnCount
        {
            let btn = buttonWithCount(i)
            sc.addSubview(btn)
        }
        sc.frame = CGRect(x:0, y:100, width:view.bounds.size.width, height: 44)
        sc.contentSize = CGSize(width:8*buttonW, height:44)
        return sc
    }
}