闭包

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
       let f = sum  //f把函数指针记录下来
        
        print(f(20,40))
        
        //最简单的闭包
        let b1 = {
            print("干掉他们")
        }
        
        b1()
        //闭包的格式 {形参列表 ->返回值类型 in 实现代码}
        
        let b2 = {
            (x:String) ->() in print(x)
        }
        b2("String")
        //带参数带返回值的闭包
        let b3 = {
            (x:Int)->Int in return x + 3
        }
        b3(4)
    }
    
    func sum(x:Int,y:Int) -> Int {
        return x + y
    }
}

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()
        //普通调用
        myFunc(strP: "hello", closureP: {
            (string) in print(string)
        })
        //尾随闭包
        myFunc(strP: "hello") {
            (string) in print(string)
        }
        
        testEscaping {
            [unowned self] ()-> Void in
            self.x = 100
        }
        print(x)
        callBackArray.first?() //修改了x
        print(x)
           }

    func myFunc(strP:String,closureP:(String)->Void) -> Void {
        closureP(strP)
    }
    var x = 10
    var callBackArray:[()->Void] = []  //定义数组 数组的元素都是闭包类型的

    // @escaping  允许逃逸出函数
    //逃逸闭包的方法
    func testEscaping(callBack:@escaping ()->Void) {
        callBackArray.append(callBack)
    }
    
}