Scala 更新記錄

class Account(val id: String, val name: String) {
    private var bal: Int = _
    
    def deposit(amount: Int) {
        require(amount > 0) // 不能存負數
        bal += amount
    }
    
    def withdraw(amount: Int) {
        require(amount > 0)     // 不能提負數
        if(amount >= bal) {
            bal -= amount
        }
        else {
            throw new RuntimeException("餘額不足")
        }
    }
    
    def balance = bal
}

class SavingAccount(val id: String, val name: String) extends Account {
    protected var bal = 0
    
    protected def balance_=(bal: Int) {
        this.bal = bal
    }

    def withdraw(amount: Int) = {
        require(amount > 0)
        if(amount < bal) {
            bal -= amount
        }
        else {
            throw new RuntimeException("餘額不足")
        }
    }
}

class Some {
    def apply(a: String) = a + " from apply...."
    def apply(a: String, b: String) = a + ", " + b + " from apply..."
    def update(a: String, b: String) = a + ", " + b + " from update..."
    def update(a: String, b: String, c: String) = 
            a + ", " + b + ", " + c + " from update..."
}

val some = new Some()
println(some("data1"))                    // data1 from apply....
println(some("data1", "data2"))           // data1, data2 from apply...
println(some("data3") = "data4")          // data3, data4 from update...
println(some("data3", "data4") = "data5") // data3, data4, data5 from update...