swift语法--12-2闭包的参数和返回值

Swift语法--12-2闭包的参数和返回值

先看一个普通的例子：在一个scrollView中添加15个button

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 1.创建UIScrollview
        let scV = UIScrollView(frame: CGRect(x: 0, y: 200, width: UIScreen.mainScreen().bounds.width, height: 50))
        scV.backgroundColor = UIColor.redColor()
        
        // 2.通过循环创建15个按钮
        let count = 15
        let width: CGFloat = 80
        let height = scV.bounds.height
        
        for i in 0..<count
        {
            let btn = UIButton()
            btn.frame = CGRect(x: CGFloat(i) * width, y: 0, width: width, height: height)
            btn.backgroundColor = UIColor.grayColor()
            
            btn.setTitle("第\(i)", forState: UIControlState.Normal)
            //将button添加到scrollView中
            scV.addSubview(btn)
            
        }
        //设置scrollView的contentSize
        scV.contentSize = CGSize(width: CGFloat(count) * width, height: height)
        
        //将scrollView添加到view上去
        view.addSubview(scV)
    }
}

需求：

• 要求创建UIScrollview以及按钮通过一个方法来创建
• 并且按钮的个数必须通过闭包来指定
• 并且如何创建按钮也必须通过闭包来指定(UIScrollview上面添加什么控件通过闭包传递)

class ViewController: UIViewController {
    override func viewDidLoad() {
        super.viewDidLoad()

        let scrollV = creatScrollV({ () -> Int in
            return 20
            }) { () -> UIButton in
                let btn = UIButton()
                btn.backgroundColor = UIColor.grayColor()
                return btn
        }
        view.addSubview(scrollV)
    }
    
    func creatScrollV (getCount:()->Int, getSingleButton: ()->UIButton)->UIScrollView{
        let scrollV = UIScrollView()
        scrollV.backgroundColor = UIColor.redColor()
        scrollV.frame = CGRect(x: 0, y: 200, width: UIScreen.mainScreen().bounds.width, height: 80)
        
        //添加按钮
        let count = getCount()  ////闭包作为参数传过来
        let height = scrollV.bounds.height
        let width:CGFloat  = 70
        
        for i in 0..<count{
            //闭包作为参数传过来
            let btn = getSingleButton()
            btn.setTitle("\(i)", forState: UIControlState.Normal)
            btn.frame = CGRect(x: CGFloat(i) * width, y: 0, width: width, height: height)
            
            scrollV.addSubview(btn)
        }
        scrollV.contentSize = CGSize(width: width * CGFloat(count), height: height)
        return scrollV
    }
}