subscripts(下标)

/*

subscripts(下标): 访问对象中数据的快捷方式

所谓下标脚本语法就是能够通过, 实例[索引值]来访问实例中的数据

类似于以前我们访问数字和字典, 其实Swift中的数组和字典就是一个结构体

Array:      subscript (index: Int) -> T

Dictionary: subscript (key: Key) -> Value?

arr[0] == arr.subscript(0)

dict["key"] == dict.subscript("key")

*/

struct Student {

var name: String = "HaRi"

var math: Double = 98.0

var chinese: Double = 99.0

var english: Double = 100.0

func score(course: String) -> Double

{

switch course {

case "math":

return math

case "chinese":

return chinese

case "english":

return english

default:

return math + chinese + english // 此处待探究为何返回nil就会爆红

}

}

//1.要想实现下标访问, 必须实现subscript方法;

//2.要想通过下标访问, 必须实现get方法;

//3.要想通过下标赋值, 必须实现set方法.

subscript(course: String) -> Double?{

get{

switch course {

case "math":

return math

case "chinese":

return chinese

case "english":

return english

default:

return math + chinese + english

}

}

set{

switch course{

case "math":

//以为返回的是可选类型

math = newValue!

case "chinese":

chinese = newValue!

case "english":

english = newValue!

default:

print("not found")

}

}

}

}

var stu = Student(name: "han", math: 99.0, chinese: 98.0, english: 57.0)

print(stu.score(course: "english"))

stu["math"] = 100.0

print(stu["math"]!)

/** Swift中是允许多索引的下标的 **/

struct Mul {

subscript(a: Int, b: Int) -> Int

{

return a + b

}

}

var m = Mul()

print(m[10,20])