Kotlin学习笔记（2）Kotlin委托代码示例

1，class委托

interface Animal{
    fun call()
}

class Cat : Animal{
    override fun call() {
        println("喵喵喵")
    }
}

class Dog : Animal{
    override fun call() {
        println("汪汪汪")
    }
}
//委托实现策略模式
//MagicAnimal行为由传入的Animal实例实现
class MagicAnimal(val animal: Animal) : Animal by animal

fun main(args: Array<String>){
    println("output:")
    MagicAnimal(Dog()).call()
    MagicAnimal(Cat()).call()
}

output:
汪汪汪
喵喵喵

2，属性委托

//委托实现策略模式
//MagicAnimal行为由传入的Animal实例实现
class MagicAnimal(val animal: Animal) : Animal by animal {
    //name属性访问由代理PropertyDelegation处理
    var name: String by PropertyDelegation()
}

class PropertyDelegation{
    private lateinit var name : String

    operator fun getValue(thisRef: Any?, property: KProperty<*>): String{
        println("name=$name")
        return name
    }

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String){
        println("value=$value")
        name = value
    }
}

fun main(args: Array<String>){
    println("output:")
    var mCat = MagicAnimal(Cat())
    mCat.name = "花花"
}

output:
value=花花