class-transformer的plainToClass：如何使用此函数将普通文字转换为抽象类？

Question

每当我这样调用plainToClass时：

someClass: SomeClass = plainToClass(SomeClass, somePlain)

一切都很好。但是一旦我将SomeClass更改为抽象并将以上内容重写为：

someAbstractClass: SomeAbstractClass = plainToClass(SomeAbstractClass, somePlain)

我收到错误：

No overload matches this call.
  Overload 1 of 2, '(cls: ClassType<BaseFeature>, plain: unknown[], options?: ClassTransformOptions): BaseFeature[]', gave the following error.
    Argument of type 'typeof BaseFeature' is not assignable to parameter of type 'ClassType<BaseFeature>'.
      Cannot assign an abstract constructor type to a non-abstract constructor type.
  Overload 2 of 2, '(cls: ClassType<SomeAbstractClass>, plain: object, options?: ClassTransformOptions): SomeAbstractClass', gave the following error.
    Argument of type 'typeof SomeAbstractClass' is not assignable to parameter of type 'ClassType<SomeAbstractClass>'

是否不可能使用plainToClass将Plain转换为abstractClass实例？为什么不呢？

Answer 1

问题是普通类和抽象类在TS中具有不同的签名：

export interface AbstractType<T> extends Function {
  prototype: T;
}

export type Type<T> = new (...args: any[]) => T;

由于这种差异，TS显示了错误。

通常不应该有抽象类的实例，只有实现它们的类的实例。不过，您可以使用any入侵它并获得所需的行为：

const someAbstractClass: SomeAbstractClass = plainToClass(
  SomeAbstractClass as any, // cast to fix the error.
  somePlain,
);