Swift函數類型

標籤：swift函數類型

    函數可以作為一種類型使用，作為類型與其它資料類型沒有區別：

    有如下3個函數的定義：

    (1)func rectangleArea(width : Double, height : Double ) -> Double {

            let area = width * height

            return area

}

      (2)func triangleArea(bottom : Double, height : Double ) -> Double {

            let area = 0.5 * bottom *  height

            return area

}

        (3)func sayHello(){

            println("Hello World")

}

        第一個和第二個函數的傳回型別都是(Double,Double) -> Double,第三個函數返回的類型為() ->()

        函數作為參數類型使用：可以把函數的類型作為另一個函數的傳回型別使用：

        樣本：

            

         func rectangleArea(width : Double, height : Double ) -> Double {

            let area = width * height

            return area

}

        func triangleArea(bottom : Double, height : Double ) -> Double {

            let area = 0.5 * bottom *  height

            return area

}

             func getArea(type : String) -> (Double,Double) ->Double {

                        var returnFunction :(Double,Double) -> Double

                            switch type {

                                case "rect":

                                        returnFunction = rectangleArea

                                case "tria" :

                                        return triangleArea

                                default:

                                        returnFunction = rectangleArea

}

                            return returnFunction

}

                var area = getArea("tria")

                println("TriangleArea:\(area(20,30))")

                

                var area = getArea("rect")

                println("TriangleArea:\(area(20,30))")

        可以把函數類型作為其它函數的參數類型使用：

            

        樣本：

            

     func rectangleArea(width : Double, height : Double ) -> Double {

            let area = width * height

            return area

}

        func triangleArea(bottom : Double, height : Double ) -> Double {

            let area = 0.5 * bottom *  height

            return area

}

          func getAreaByFunc(funcName : (Double,Double) -> Double, a: Double,b: Double) -> Double {

                var area = funName(a,b)

                return area

}

            var result :Double = getAreaByFunc(rectangleArea,20,30)

                

本文出自 “平凡之路” 部落格，請務必保留此出處http://linjohn.blog.51cto.com/1026193/1620360

Swift函數類型