There are three base implementations provided for sub-classing.

所提供的用于生成子类的基本实现有三种。

youdao

In VB this is relatively easy to achieve, so long as you understand sub-classing.

在VB这是比较容易实现的，只要你明白分分级。

youdao

After 24 pages we reach a much better design, which mainly USES a map to store properties rather than sub-classing for each type of instrument.

在24页之后，我们看到了更好的设计，主要用map来存储属性，而不是为每种乐器类型建立子类。

youdao