google kotlin 训练营-泛型

原文

class MyList<T> {
fun get(pos: Int): T {
TODO("implement")
}
fun addItem(item: T) {}
}

默认 T 可为 null
相当于

class MyList<T:Any?> {
fun get(pos: Int): T {
TODO("implement")
}
fun addItem(item: T) {}
}

如果想不为null,则

class MyList<T:Any> {
fun get(pos: Int): T {
TODO("implement")
}
fun addItem(item: T) {}
}

check
如果waterSupply.needsProcessing为true,则抛出异常

class Aquarium<T: WaterSupply>(val waterSupply: T) {
fun addWater() {
check(!waterSupply.needsProcessing) { "water supply needs processing first" }
println("adding water from \$waterSupply")
}  
}

泛型函数

fun <T: WaterSupply> isWaterClean(aquarium: Aquarium<T>) {
   println("aquarium water is clean: ${!aquarium.waterSupply.needsProcessing}")
}

泛型方法

inline fun <reified R: WaterSupply> hasWaterSupplyOfType() = waterSupply is R

扩展函数

inline fun <reified R: WaterSupply> Aquarium<*>.hasWaterSupplyOfType() = waterSupply is R

inline fun <reified R: WaterSupply> Aquarium<*>.hasWaterSupplyOfType() = waterSupply is R