C＃抽象类 [英] c# abstract classes

问题描述

我要创建一个计算年费，商业和私人车辆假DMV程序。这两个类将是抽象的，他们会从一个叫所有车辆类多态。

i have to create a fake DMV program that calculates annual fees, for commercial and private vehicles. Those two classes will be abstract and they will polymophism from a class named all vehicles.

我的教练希望只有一个对象创建的整个程序（主），但因为我的顶级3层类是抽象的。我无法和他们创建一个对象，即车辆=新车（）;

My instructor wants only one object created the entire program(in main) but since my top 3 tier classes are abstract. I can't create an object with them i.e. vehicles = new vehicles();

所以我的问题是我如何创建只有一个对象，因为它们是抽象的？如果您有任何问题随时问，我可能没有解释这口井......

so my question is how do i create only one object since they are abstract? If you have any questions feel free to ask, I might have not explained this well...

推荐答案

您的阶级结构会看是这样的：

Your class structure will look something like:

abstract class Vehicle
{
    protected abstract int BaseFee { get; }
    protected abstract int ExtraFee { get; }

    public int CalculateFee()
    {
        return BaseFee + ExtraFee;
    }
}

abstract class CommercialVehicle : Vehicle
{
    protected override int BaseFee
    {
        return 100;
    }
}

class LightDutyTruck : CommercialVehicle
{
    protected override int ExtraFee
    {
        return 50;
    }
}

class Semi : CommercialVehicle
{
    protected override int ExtraFee
    {
        return 150;
    }
}

[etc...]

abstract class PrivateVehicle : Vehicle
{
    protected override int BaseFee
    {
        return 25;
    }
}

class Sedan : PrivateVehicle
{
    protected override int ExtraFee
    {
        return 15;
    }
}

和等，为每个类。在你的主方法，你会根据输入创建实例，但你的实际变量将被声明为类型车 。实际计算将根据您创建实例生效：

and so on, for each class. In your Main method, you would create the instance based on input, but your actual variable would be declared as type Vehicle. The actual calculation will take effect based on the instance that you create:

Vehicle v;
switch(input)
{
    case "semi":
        v = new Semi();
        break;
    case "truck":
        v = new LightDutyTruck();
        break;
    ...
}

int fee = v.CalculateFee();

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