Swift中闭包

1.闭包

可以通过定义属性或者定义方法进行回调的操作

1️⃣无参无返回值

typealias funcBlock = () -> ()

(1)定义属性

var parameterBlock : funcBlock?
if parameterBlock != nil{
    parameterBlock!();
}

对应的调用

 block.parameterBlock = {() -> () in
     print("无参无返回值")
 }

(2)定义成方法

 func testBlock(blockfunc: funcBlock!){
        if (blockfunc) != nil{
            blockfunc() 
        }
  }

对应的调用

 block.testBlock {
      print("-------func--------")
 }

2️⃣有参无返回值

   typealias callBackBlock = (_ index : String ) -> ()         
    
   func callBackFuncBlock(blockfunc: callBackBlock!) {
        if blockfunc != nil{
            blockfunc("I am Amy")
        }
    }

对应的回调

  block.callBackFuncBlock { (res: String) in
         print(res);
   }
//打印结果:I am Amy

3️⃣有参数有返回值

   typealias paramBlock = (Int) -> String           //返回值类型是字符串

    func paramFuncBlock(blockfunc: paramBlock!) {
        if blockfunc != nil{
            let retFunc = blockfunc(5)
            print("Block\(retFunc)")
            
        }
    }

对应的回调

     block.paramFuncBlock { (res: Int) -> String in
            return "res: \(res)*50"
      }

4️⃣返回值是一个函数指针，入参为String

   typealias funcBlockB = (Int,Int) -> (String)->()

    func testBlockB(blockfunc: funcBlockB!) {
        if blockfunc != nil {
            let retFunc = blockfunc(9,10)
            retFunc("The Result is")
        }
    }

对应的回调

   block.testBlockB { (a: Int, b:Int) -> (String) -> () in
         func callBackFunc(res: String) {
             print("\(res) : \(a) + \(b) = \(a+b)")
         }
         return callBackFunc
   }
//打印结果:The Result is : 9 + 10 = 19

5️⃣返回值是一个函数指针，入参为String 返回值也是String

    typealias funcBlockC = (Int,Int) -> (String)->String
    func testBlockC(blockfunc: funcBlockC!) {
        if (blockfunc) != nil {
            let retfunc = blockfunc(9,10)
            let str = retfunc("The Result is")
            print("\(str)")
        }
  
    }

对应的回调

block.testBlockC { (a: Int, b: Int) -> (String) -> String in
     func sumFunc(res: String) -> String {
                let resNum = a + b
                return "\(res)  \(a) + \(b) = \(resNum)"
            }
            return sumFunc
  }
//打印结果: The Result is  9 + 10 = 19

以上🍓