一、计算属性的概念
计算属性本身不存储数据，而是从其它存储属性中计算得到数据，与存储属性不同，类、结构体、和枚举都可以定义计算属性
计算属性提供了一个getter来获取值，以及一个可选的setter来间接设置其它属性或变量的值，计算属性的语法如下：
面向对象类型 类型名{
存储属性...
var 计算属性名：属性数据类型{
get {
return 计算后属性值
}
set 新属性值{
}
}
示例:
class Employee {
var no:Int = 0
var firstName:String = ""
var lastName:String = ""
var job:String?
var salary:Double = 0
lazy var dept:Department = Department()
var fullname:String{
get{
return firstName+"."+"lastName"
}
set(newFullName)系统默认给的变量名为newvalue{
var name = newFullName.componentsSeperatedByString(".")
firstName = name[0]
lastName = name[1]
}
}
}二、只读计算属性
计算属性可以只有getter访问器，没有setter访问器，这就是只读计算属性
示例：
class Employee {
var no:Int = 0
var firstName:String = ""
var lastName:String = ""
var job:String?
var salary:Double = 0
lazy var dept:Department = Department()
var fullname:String{
get{
return firstName+"."+"lastName"
}
}
}三、结构体和枚举中的计算属性
示例
struct Department {
let no:Int = 0
var name : String = "sales"
var fullName:String {
return "swift" + name + ".D"
}
}
var dept = Department()
println(dept.fullName)
enum WeekDays:String {
case Monday = "Mon"
case Tuesday = "Tue"
case Wednesday = "Wed"
case Thursday = "Thu"
case Friday = "Fri"
var message:String {
return "Today is"+self.rawValue
}
}
var day = WeekDays.Monday
println(day.message)
本文出自 “平凡之路” 博客，请务必保留此出处http://linjohn.blog.51cto.com/1026193/1621924
原文：http://linjohn.blog.51cto.com/1026193/1621924