Delphi 中的抽象类 [英] Abstract Class in Delphi

问题描述

我正在使用一个包含许多抽象类的组件套件.现在我想应用多态性，但是当我创建对象时出现错误抽象类.

I am using a component suite which has many abstract classes. Now I want to apply polymorphism but I am getting Error Abstract Class when I create my object.

我是否应该覆盖所有虚拟方法，即使我不需要它?有什么变通办法或解决方案吗?

Should I override all methods which are virtual even if I don't need it? Are there any workaround or solution?

推荐答案

为了创建类的实例，您需要覆盖所有声明为虚拟抽象的方法.即使你不使用它们.

In order to make an instance of a class, you need to override all methods that are declared as virtual abstract. Even if you don't use them.

如果你真的想要变通，你可以使用空方法.但我不建议这样做.

If you really want a work around, you can use empty methods. But I won't recommend that.

并添加有关该主题的更多信息:

And to add some more information on the subject:

如果方法是用虚抽象声明的，那么它就是抽象的:

A method is abstract if it is declared with virtual abstract:

procedure MyMethod(const AMyParameter: Integer); virtual; abstract;

琐事:您甚至可以将方法重写为抽象方法:

Trivia: You can even override a method as abstract:

procedure MyMethod(const AMyParameter: Integer); override; abstract;

您需要覆盖这些方法才能从该类实例化.

You need to override these methods in order to instantiate from that class.

并且您可以将整个类声明为抽象类:

And you can declare an entire class as abstract:

type
  TMyClass = class abstract (TMyAncestor)
  end;

如果您尝试实例化该类，则会收到警告.

You get a warning if you try to instantiate that class.

对应的是一个密封类:

type
  TMyClass = class sealed (TMyAncestor)
  end;

如果您尝试从该类继承，则会收到警告.

You get a warning if you try to inherit from that class.

您也可以密封方法，但为此您需要关键字 final.

You can also seal methods, but you need the keyword final for that.

procedure MyMethod(const AMyParameter: Integer); override; final;

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