CODEWITHSUNDEEP
angulartypescripttslinttypescript3.0
netdjw
netdjw

Reputation: 5997

Property 'parse' does not exist on type 'new () => T'

I'm working on a general data service in Angular witch can handle data models and communicate with backend.

Now I have multiple services to each API endpoints, same code, just the model type (and of course the URI) is the difference.

I started develop a multipurpose service on this way:

Here is BaseModel to define most basic things on models, models/base_model/base.model.ts:

export class BaseModel {
  id: number;
  prepareToSave: () => void;
  static parse () {
    throw new Error('not implemented');
  }
}

Here is a Photoalbum model to define a data set, models/photoalbum/photoalbum.model.ts:

export class Photoalbum {
  id: number;
  public: boolean;
  name: string;

  static parse(data: any) {
    return new this(data);
  }

  prepareToSave() {
    return {
      // convert datas to backend
    }
  }
}

Here is the DataService to communicate the backend, services/data/data.service.ts:

export class DataService<T extends BaseModel> {
  constructor(
    private type: new () => T,
    private url: string,
    private http: HttpClient) { }

  getAll(): Promise<T[]> {
    return new Promise( resolve => {
      this.http.get(this.url).subscribe( (result: any) => {
        const data: T[] = [];
        result.forEach( (item: any) => {
          data.push(this.type.parse(item)); // error in this line
        });
        resolve(data);
      });
    });
  }

  // ...
}

Now I get this error in DataService:

Property 'parse' does not exist on type 'new () => T'.

I'm using TypeScript 3.5.2 with tslint 5.9.1 if this is relevant.

Is there any idea how to fix this?

Upvotes: 2

Views: 2674

Answers (1)

GOTO 0
GOTO 0

Reputation: 47614

Well, parse only exists as a static property of BaseModel, so it's no surprise that you are receiving an error. Change the type of type in the constructor.

  constructor(
    private type: { new (): T, parse(data: any): any },
    private url: string,
    private http: HttpClient) { }

Then update the definition of the parse method to accept one argument.

export class BaseModel {
  id: number;
  prepareToSave: () => void;
  static parse (item: any): any {
    throw new Error('not implemented');
  }
}

Upvotes: 1

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