C# 无法从抽象 parent class object 访问 child public 方法

Question

我正在学习 OOAD 并尝试实现 class 与继承的关系，但这里有一个问题是代码

Parent Class

namespace ConsoleApplication1
{
    abstract class Classification
    {
        public abstract string type();
    }
}

第一ChildClass

namespace ConsoleApplication1
{
    class FullTime : Classification
    {
        bool inCampus;
        string roomDetail;
        float rent;

        public FullTime(string studentRoomDetail, float studentRent)
        {
            this.inCampus = true;
            this.roomDetail = studentRoomDetail;
            this.rent = studentRent;
        }

        public FullTime()
        {
            this.inCampus = false;
        }

        public string printAccommodationDescription()
        {
            if (!this.inCampus)
            {
                return "Not in campus";
            }
            else
            {
                return "Room: " + this.roomDetail + " Rent: " + this.rent.ToString();
            }
        }

        public override string type()
        {
            return "fulltime";
        }
    }
}

第二个ChildClass

namespace ConsoleApplication1
{
    class PartTime : Classification
    {
        bool onJob;
        string jobTitle;
        float salary;

        public PartTime(string studentJobTitle, float studentSalary)
        {
            this.onJob = true;
            this.jobTitle = studentJobTitle;
            this.salary = studentSalary;

        }

        public PartTime()
        {
            this.onJob = false;
        }

        public string printJobDescription()
        {
            if (!this.onJob)
            {
                return "Not on job";
            }
            else
            {
                return "JobTitle: " + this.jobTitle + " Salary: " + this.salary.ToString();
            }
        }

        public override string type()
        {
            return "parttime";
        }
    }
}

现在在 Program.cs 中，当我尝试从 PartTime class

访问方法 printJobDescription 时

Classification classification = new PartTime("Software Engineer", 10000);
classification.printJobDescription();

它说

Error CS1061 'Classification' does not contain a definition for 'printAccommodationDescription' and no extension method 'printAccommodationDescription' accepting a first argument of type 'Classification' could be found (are you missing a using directive or an assembly reference?)

我该如何解决这个问题？

更新

我需要让 object 在运行时更改其 class 的能力，因此我必须创建 Classification 类型的 object 并使用以下任一方法未在其他 class

中实施

Answer 1

将您的对象转换为另一种对象类型时，称为 Polymorphism。这意味着您只能使用暴露给目标对象类型的方法和属性，该类型 Classification 不知道您的方法。

我做的简单例子：

using System;

namespace Program
{
    public class Program
    {
        public static void Main()
        {
            Dog rex = new Dog();
            Animal rexAsAnimal = rex;

            // Can access 'MakeSound' due the fact it declared at Dog (Inherited by Animal)
            Console.WriteLine(rex.MakeSound()); // Output: Bark

            // Compilation error: rexAsAnimal is defined as 'Animal' which doesn't have the 'Bark' method.
            //Console.WriteLine(rexAsAnimal.Bark()); // Output when uncomment: Compilation error.

            // Explicitly telling the compiler to cast the object into "Dog"
            Console.WriteLine(((Dog)rexAsAnimal).Bark()); // Output: Bark
        }
    }

    public abstract class Animal
    {
        public abstract string MakeSound();
    }

    public class Dog : Animal
    {
        public override string MakeSound() { return Bark(); }
        public string Bark()
        {
            return "Bark";
        }
    }
}

Answer 2

您只能使用在您使用的 class 中声明的函数。

abstract class Classification
{
  public abstract string type();
}

class PartTime : Classification
{
  public override string type() {...}
  public Job1() {...}
}

class FullTime : Classification
{
  public override string type() {...}
  public Job2() {...}
}

Classification类型的对象只能使用type()
PartTime 类型的对象可以使用类型和 Job1()
FullTime 类型的对象可以使用类型和 Job2()

如果你有这样的对象：

Classification classification = new PartTime();

而且您不知道是哪种特殊类型，您必须强制转换此对象才能使用其他方法：

if (classification is PartTime)
{
  ((PartTime)classification).Job1();
}
else if (classification is FullTime)
{
  ((FullTime)classification).Job2();
}

希望对您有所帮助。

C# 无法从抽象 parent class object 访问 child public 方法

C# Cannot access child public method from abstract parent class object

c#

inheritance

abstract-class

class-relationship