使用TypeScript时，扩展Node.js客户端库中的“ conv”实例以在Google v2上执行操作

Question

In the Actions on Google Node.js client library v2 there is a middleware that allows to add properties or helper classes to the conv instance. An Example from the official version 1 migration guide:

const { dialogflow } = require('actions-on-google');

class Helper {
  constructor(conv) {
    this.conv = conv;
  }

  func1() {
    this.conv.ask(`What's up?`);
  }
}

const app = dialogflow()
  .middleware(conv => {
    conv.helper = new Helper(conv);
  });

app.intent('Default Welcome Intent', conv => {
  conv.helper.func1();
});

This may work fine for plain JavaScript. But what if TypeScript is used?

If the code is written in Typescript, TSC complains about the lines conv.helper = new Helper(conv); and conv.helper.func1(); :

[ts] Property 'helper' does not exist on type 'DialogflowConversation<{}, {}, Contexts>'.

Maybe I could rewrite it to (<any>conv).helper , but that's pretty ugly. Does anyone know a (better) solution?

Answer 1

The dialogflow app creation function is overloaded with generic type parameters that allow you to override the Conversation type sent through the intent handler.

You just need to create a type extending the appropriate Conversation type. It is much more complicated in order to keep all the type security but it's doable.

So the snippet you shared in TypeScript in the most type secure and generic implementation would be:

import {
  dialogflow,
  DialogflowConversation,
  DialogflowMiddleware,
  Contexts,
} from 'actions-on-google';

// an interface with the extensions to the Conversation type
interface HelperConversation<
  TData = {},
  TUserStorage = {},
  TContexts extends Contexts = {},
> extends DialogflowConversation<TData, TUserStorage, TContexts> {
  helper: Helper<TData, TUserStorage, TContexts>;
}

// the helper class now passing generic type parameters from the Conversation type
class Helper<TData, TUserStorage, TContexts extends Contexts> {
  constructor(public conv: DialogflowConversation<TData, TUserStorage, TContexts>) {}

  func1() {
    this.conv.ask(`What's up?`);
  }
}

// to keep type security in the middleware, it needs to be functional and of the DialogflowMiddleware type
const middleware: DialogflowMiddleware<HelperConversation> =
  conv => Object.assign(conv, { helper: new Helper(conv) })

// pass the extended Conversation interface into the `dialogflow` function
const app = dialogflow<HelperConversation>()
  .middleware(middleware);

app.intent('Default Welcome Intent', conv => {
  // now conv is of the type `HelperConversation`
  conv.helper.func1();
});

Depending on how secure/generic you want the TypeScript middleware to be, you can get rid of a lot of the extra generic parameters with basic Object types which cuts back on a lot of the code.

You can also take a look at the TypeScript code snippets shared during the alpha for more detailed usages of TypeScript with the library:

• Example TypeScript Plugin
• Example TypeScript Plugin Usage