A TypeScript class that is a concrete implementation of a generic type

When handling a login operation, I receive an HTTP response like this:

interface ILoginResponse {   // ok
  message: string
  token: string;
}

This response structure is part of a generic response format that I intend to use for all my HTTP responses:

interface IResponse<TResponseData> {    // ok
  Data: TResponseData;
  Errors: string[];
  Status: number;
}

My plan was to incorporate this generic response format into an abstract service like so:

abstract class HttpService<TRequest, IResponse<TResponseData>> {   // ERROR
  protected onSuccess(responseData: TResponseData);  // I want to do this (hide the wrapper from the subclass)
}

I had hoped to extend this abstract service for different HTTP operations, such as a login operation:

class LoginService extends HttpService<ILoginRequest, ILoginResponse> { }  // ok

However, I encountered an issue in the HttpService class:

"Cannot find name 'TResponseData'"
.

How can I resolve this?

Answer №1

To restrict the second argument, you can make it so that it must extend IResponse:

abstract class HttpService<TRequest, TResponse extends IResponse<any>> { }

Alternatively, you could utilize TResponseData and implement IResponse<TResponseData> whenever you require the response:

abstract class HttpService { 
    doRequest(request: TRequest): IResponse<TResponseData>
}

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