在学习中 看见了willset 这个词就去查了一下
class People : NSObject
{
//普通属性
var firstName:String = ""
var lastName:String = ""
var nickName:String = ""
//计算属性
var fullName:String
{
get
{
return nickName + " " + firstName + " " + lastName
}
}
//带属性监视器的普通属性
var age:Int = 0
{
//我们需要在age属性变化前做点什么
willSet
{
print("Will set an new value (newValue) to age")
}
//我们需要在age属性发生变化后，更新一下nickName这个属性
didSet
{
print("age (oldValue) to (age)")
if age<10
{
nickName = "Little"
}else
{
nickName = "Big"
}
}
}
func toString() -> Strin{
return "Full Name: (fullName) " + ", Age: (age) "
}
}
var me = People()
me.firstName = "li"
me.lastName = "qian"
me.age = 20
print(me.toString())
