（十五）Kotlin简单易学 基础语法-类继承与重载open关键字

（十五）Kotlin简单易学 基础语法-类继承与重载open关键字

继承

类默认都是封闭的，要让某个类开发继承，必须使用open关键字修饰它。

open class Product(var name:String) {fun description()= "Product: $name" //open关键字修饰它，子类才可以重写open fun load() = "Noting.."
}// //open关键字修饰它，子类才可以继承
class LuxuryProduct :Product("Luxury"){//覆盖overrideoverride fun load() = "Luxury loading"
}fun main() {val p:Product = LuxuryProduct()//Luxury loadingprint(p.load())
}

类型检测

Kotlin的is运算符是个不错的工具，可以用来检查某个对象的类型

open class Product(var name:String) {fun description()= "Product: $name"open fun load() = "Noting.."
}class LuxuryProduct :Product("Luxury"){//覆盖overrideoverride fun load() = "Luxury loading"
}fun main() {val p:Product = LuxuryProduct()//输出trueprint(p is Product)//输出trueprint(p is LuxuryProduct)//输出falseprint(p is File)}

类型转换

open class Product(var name: String) {fun description() = "Product: $name"open fun load() = "Noting.."
}class LuxuryProduct : Product("Luxury") {//覆盖overrideoverride fun load() = "Luxury loading"fun special() = "LuxuryProduct special function"
}fun main() {val p: Product = LuxuryProduct()//输出LuxuryProduct special function//类型转换if (p is LuxuryProduct) {print(p.special())}
}

智能类型转换

Kotlin编译器很聪明，只要能确定any is 父类条件检查属实，它就会将any当作字类对象对待，因此 编译器允许你不经类型转换直接使用。

open class Product(var name: String) {fun description() = "Product: $name"open fun load() = "Noting.."
}class LuxuryProduct : Product("Luxury") {//覆盖overrideoverride fun load() = "Luxury loading"fun special() = "LuxuryProduct special function"
}fun main() {val p: Product = LuxuryProduct()//输出LuxuryProduct special functionprint((p as LuxuryProduct).special())
}

Kotlin层次

无须在代码里显示指定，每一个类都会继承一个共同的叫做Any的超类。

open class Product(var name: String) {fun description() = "Product: $name"open fun load() = "Noting.."
}class LuxuryProduct : Product("Luxury") {//覆盖overrideoverride fun load() = "Luxury loading"fun special() = "LuxuryProduct special function"
}fun main() {val p: Product = LuxuryProduct()//输出trueprint(p is Any)
}

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