Question

通过组合接口来创建具有可区分字段的类型？

这是我的代码：

/*
 * Missing changeFn indicates delete
 */
type IChangeRequestPromiseProxy<TEntity extends IBaseEntity> =
    | IUpdateRequestPromiseProxy<TEntity>
    | IDeleteRequestPromiseProxy;

interface IUpdateRequestPromiseProxy<TEntity extends IBaseEntity> {
    id: Id;
    resolve(value: IPersistence<TEntity>): void;
    reject(reason: any): void;
    changeFn(entity: TEntity): IPersistence<TEntity>;
}

interface IDeleteRequestPromiseProxy {
    id: Id;
    resolve(value: void): void;
    reject(reason: any): void;
    changeFn(entity: never): never;
}

let promiseProxy: IChangeRequestPromiseProxy<TEntity> = { id, resolve, reject };

这是我得到的错误。要点似乎是Property 'changeFn' is missing in type：

让promiseProxy：IChangeRequestPromiseProxy类型'{id：串;解决：（值？：IPersistence | PromiseLike> |未定义）=> void;拒绝：（原因？：任意）=>无效； }'无法分配给type “ IChangeRequestPromiseProxy”。属性“ changeFn”为缺少类型'{id：string;解决：（值？：IPersistence | PromiseLike> |未定义）=> void;拒绝：（原因？：任意）=>无效； }'，但必须输入 'IUpdateRequestPromiseProxy'.ts（2322）Queue.service.ts（16， 5）：在此处声明“ changeFn”。

为什么不起作用？

Answer 1

changeFn(entity: never): never;没有使属性changeFn成为可选属性。要使其可选，您可以使用?对其进行声明，并且由于您实际上不需要此处的任何值，因此其类型应为undefined

从您的问题中添加缺少的类型看起来像：

type IChangeRequestPromiseProxy<TEntity extends IBaseEntity> =
    | IUpdateRequestPromiseProxy<TEntity>
    | IDeleteRequestPromiseProxy;

interface IUpdateRequestPromiseProxy<TEntity extends IBaseEntity> {
    id: Id;
    resolve(value: IPersistence<TEntity>): void;
    reject(reason: any): void;
    changeFn(entity: TEntity): IPersistence<TEntity>;
}

interface IDeleteRequestPromiseProxy {
    id: Id;
    resolve(value: void): void;
    reject(reason: any): void;
    changeFn?:undefined;
}

interface IBaseEntity {}
class Entity { }
interface IPersistence<T> { o: T}
type Id = string;
declare const id: string;
declare const resolve: (value: void) =>  void;
declare const reject: (value: any) =>  void;

let promiseProxy: IChangeRequestPromiseProxy<Entity> = { id, resolve, reject };

通过组合接口来创建带有区分字段的类型？

1 个答案: