如何在定义为"any"的第三方TypeScript接口内增加属性? [英] How can I augment a property within a third-party TypeScript interface defined as "any"?

问题描述

给出如下定义的第三方TypeScript模块:

Given a third-party TypeScript module defined like this:

// in /node_modules/third-party-module/index.d.ts
declare module 'ThirdPartyModule' {
    export interface ThirdPartyInterface {
        data: any;
    }
}

如何增强此模块以更严格地键入data属性?

How can I augment this module to more strictly type the data property?

我已经尝试过了:

// in /app/typings.d.ts
declare module 'ThirdPartyModule' {

    interface IMyCustomType {}

    interface ThirdPartyInterface {

        // causes a compiler error: Subsequent property declarations 
        // must have the same type.  Property 'data' must be of type 
        // 'any', but here has type 'IMyCustomType'.
        data: IMyCustomType;
    }
}

但是这给了我一个编译器错误:后续属性声明必须具有相同的类型.属性'data'必须具有'any'类型，但是此处具有'IMyCustomType'类型."

But this gives me a compiler error: "Subsequent property declarations must have the same type. Property 'data' must be of type 'any', but here has type 'IMyCustomType'."

如果第三方模块改为将该属性定义为实际类型，则如下所示:

If the third-party module instead defined the property as an actual type, like this:

// in /node_modules/third-party-module/index.d.ts
declare module 'ThirdPartyModule' {
    interface IAnotherThirdPartyInterface {
        something: string;
    }

    interface ThirdPartyInterface {
        data: IAnotherThirdPartyInterface;
    }
}

我可以简单地使我的IMyCustomType界面扩展此第三方类型:

I could simply make my IMyCustomType interface extend this third party type:

// in /app/typings.d.ts
declare module 'ThirdPartyModule' {
    interface IMyCustomType extends IAnotherThirdPartyInterface {}

    interface ThirdPartyInterface {
        data: IMyCustomType;
    }
}

但是，由于类型定义为any，因此我无法对其进行扩展:

However, since the type is defined any, I can't extend it:

// causes a compiler error:  'any' only refers to a type, 
// but is being used as a value here.
interface IMyCustomType extends any {}

推荐答案

虽然您无法重新定义属性，但是另一种方法是定义一个新属性，并使用该新属性扩展原始对象.虽然此解决方案通常不适用，但是如果属性在类上，则可以完成.在您的情况下，您在注释hapi中提及.由于该属性位于Server类上，因此我们可以定义该属性的新类型版本.

While you can't redefine the property, an alternative would be to define a new property, and augment the original object with this new property. While this solution is not generally applicable, if the property is on a class it can be done. In your case you mention in the comments hapi. Since the property is on the Server class we can define a new typed version of the property.

hapi.augment.ts

import *  as Hapi from 'hapi'

declare module 'hapi' {
    export function server(cfg: any): Hapi.Server;
    interface Server {
        typedApp:  {
            myData: string
        }
    }
}

Object.defineProperty(Hapi.Server.prototype, 'typedApp', {
    enumerable: false,
    get(this: Hapi.Server){
        return this.app;
    },
    set(this: Hapi.Server, value: any){
        this.app = value;
    }
});

usage.ts

import *  as Hapi from 'hapi'
import './hapi.augment'

const server = new Hapi.Server()
server.connection({ port: 3000, host: 'localhost' });
server.start();
server.typedApp.myData = "Here";

server.route({
    method: 'GET',
    path: '/',
    handler: function (request, reply) {
        reply(request.server.typedApp.myData);
    }
});

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