Kotlin基本继承解决方案

Question

如何使用owner和balance的初始值制作新的SavingAccount

open class BankAccount(val owner: String = "Long John Silver", private var balance: Double = 0.00) {
    constructor (amount: Double) : this() {
        this.balance = amount
    }
    fun deposit(amount: Double){
        this.balance += amount
    }
    fun withdraw(amount: Double){
        this.balance -= amount
    }
    fun getBalance(): Double{
        return this.balance
    }
}

和孩子班

class SavingAccount(val increasedBy: Double = 0.05): BankAccount(){
    fun addInterest(): Unit{
        val increasedBy = (this.getBalance() * increasedBy)
        deposit(amount = increasedBy)
    }
}

，在Main

中

fun main(args: Array<String>) {
    val sa = SavingAccount();// how to do this SavingAccount("Captain Flint", 20.00)
    println(sa.owner)
    println(sa.owner)
}

如何为新用户创建SavingAccount，而无需默认值？

Answer 1

您可以使用普通的构造函数 - arguments(因此没有属性(实现它，并将其传递到您的BankAccount

中

class SavingAccount(owner: String,
        balance: Double,
        val increasedBy: Double = 0.05
): BankAccount(owner, balance) {
}

SavingAccount的默认值可以定义类似于BankAccount：

class SavingAccount(owner: String = "Default Owner",
        balance: Double = 0.0,
        val increasedBy: Double = 0.05
): BankAccount(owner, balance) {
}

Answer 2

将您的类声明更改为

class SavingAccount(owner: String, 
                    balance: Double, 
                    val increasedBy: Double = 0.05): BankAccount(owner, balance)