“无法创建抽象类或接口的实例” C# 错误消息

发布于 2024-10-16 19:31:14 字数 228 浏览 2 评论 0原文

我将项目的基类更改为 abstract，现在收到以下错误：

无法创建抽象类或接口的实例

我收到错误是因为不允许命名 abstract 类的新实例吗？

newPlane = new Airplane_Abstract(name, position);

原文

I changed my base class to abstract for a project and now I'm receiving the following error:

Cannot create an instance of the abstract class or interface

Am I receiving the error because naming a new instance of an abstract class is not allowed?

newPlane = new Airplane_Abstract(name, position);

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对风讲故事 2024-10-23 19:31:14

您无法创建抽象类的实例。将其视为也可能包含一些实现逻辑的接口。如果您调用没有定义的抽象实例方法，您会期望发生什么？

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难得心□动 2024-10-23 19:31:14

我看到你之前的问题，其中你询问了“纯虚拟”（C# 中的abstract）的含义。

无法实例化抽象类的原因是它可能具有抽象成员，但没有实现。所以说你的类看起来像这样：

abstract class Airplane_Abstract
{
    public abstract int GetSomeInteger();
}

然后假设你可以实例化其中一个，你可以编写如下代码：

var airplane = new Airplane_Abstract();

// What would this be?
int integer = airplane.GetSomeInteger();

当然，我不相信你实际上拥有在抽象类中拥有抽象成员。但抽象类的一般思想是它不能单独存在；它不能独立存在。它必须在继承它的类中进一步定义。抽象成员最明显地说明了为什么会出现这种情况；可能还有其他原因。

例如，考虑一下形状。这是一个非常常见的例子，作为抽象类是有意义的。您不能真正实例化只是一个Shape，对吗？（“创建一个形状。”“什么样的形状？”“没有种类。只是一个抽象的形状。”实际上不起作用，不是吗？）

I saw your earlier question, in which you asked about the meaning of "pure virtual" (abstract in C#).

The reason you cannot instantiate an abstract class is that it presumably has abstract members, with no implementation. So say your class looks like this:

abstract class Airplane_Abstract
{
    public abstract int GetSomeInteger();
}

Then assuming you could instantiate one of these, you could write code like this:

var airplane = new Airplane_Abstract();

// What would this be?
int integer = airplane.GetSomeInteger();

Granted, I don't believe you actually have to have abstract members in an abstract class. But the general idea of an abstract class is that it's one that cannot exist on its own; it must be further defined in a class which inherits from it. Abstract members are the most obvious illustration of why this would be; there could be other reasons.

Think of Shape, for example. This is a pretty common example of something that would make sense as an abstract class. You can't really instantiate just a Shape, can you? ("Create a shape." "What kind of shape?" "No kind. Just an abstract shape." Doesn't really work, does it?)

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