kotlin - 在创建类和构造函数时期望成员声明

Question

我是 kotlin 的新手，我正在尝试在 kotlin 上应用关于 oop 的类(class), 但我得到了多个 "Expecting member declaration"

我不知道这段代码哪里出错了

open class Car( open val color:String?=null, open val brand:String?=null) {
    
    open fun speed(){
        println("max speed is 220")
    }
}

class Toyota() : Car() {
    override color = "White"
    override brand = "Toyota"
    
    override fun speed(){
        println("max speed is 360")
    }
}


fun main() {
   
    var car:Toyota = Toyota()
    car.speed()
    
   
}

Answer 1

Toyota 类的两个参数中都缺少 val 关键字:

class Toyota() : Car() {
    override val color = "White"
    override val brand = "Toyota"

    override fun speed(){
        println("max speed is 360")
    }
}

---

或者你可以通过直接使用 Car 构造函数来做得更好:

class Toyota : Car(color = "White", brand = "Toyota") {
    override fun speed(){
        println("max speed is 360")
    }
}

使用这种方法，您甚至可以使 Car 变得更简单(不需要在您的属性上使用 open 关键字):

open class Car(val color : String? = null, val brand : String? = null) {
    open fun speed(){
        println("max speed is 220")
    }
}