Angular: defining a new class instance and implementing various services

Question

Angular: defining a new class instance and implementing various services

Creating a class called User raises the concern of having access to services within it, especially when using the constructor() for dependency injection.

Below is an implementation of the User class:

import { ElementRef, Injectable } from '@angular/core';
import { DbService } from '../service/db.service';
import { ImageService } from '../service/skin.service';

export class User {
    name: string;
    img: ElementRef<HTMLCanvasElement>;

    constructor(
        name: string,
        img?: ElementRef<HTMLCanvasElement> | string[]) {

        this.name = name;

        if (img) {
            if (img instanceof ElementRef) {
                this.img = img;
            } else {
                this.img.nativeElement = this.ImageService.render(img);
            }
        } else {
            DbService.getSkin(name).subscribe(res => this.img.nativeElement.this.service.render(res));
        }
    }
}

Rather than making required functions public static, what is the best way to incorporate DbService and ImageService into the User class?

angular typescript class

Answer 1

Answer №1

One way to improve the code is by following the principles of SOLID and dividing responsibilities effectively.

An entity called User has properties like name and img. It's recommended that the User entity does not have knowledge about the DBService.

To manage this, you can implement a factory that creates instances of User, where the factory itself is aware of the DBService. The factory could operate in two ways:

Create and provide a synchronous instance of User, then asynchronously fill the img property if needed by calling DbService.getSkin
Always create and return an asynchronous instance of User through an observable

The second option is preferred due to its more predictable behavior and avoids unexpected updates to the img property.

The revised code would look like this:

Case 1 - Return a `User` instance

interface User {
  name: string;
  img: ElementRef<HTMLCanvasElement> | string[];
}

@Injectable({providedIn: 'root')
export class UserFactory {
  constructor(private dbService: DBService) {}

  create(
    name: string,
    img?: ElementRef<HTMLCanvasElement> | string[],
  ): User {
    const user: User = {
      name,
      img,
    }

    if (!img) {
      this.dbService.getSkin(name).pipe(
        tap(someResponse => {
          /* 
            SET IMG HERE
            user.img = someResponse
          */
        }),
      ).subscribe();
    }

    return user;
  }
}

Case 2 - Return observable

interface User {
  name: string;
  img: ElementRef<HTMLCanvasElement> | string[];
}

@Injectable({providedIn: 'root')
export class UserFactory {
  constructor(private dbService: DBService) {}

  create(
    name: string,
    img?: ElementRef<HTMLCanvasElement> | string[],
  ): Observable<User> {
    const user: User = {
      name,
      img,
    }

    let user$: Observable<User> = of(user);

    if (!img) {
      user$ = this.dbService.getSkin(name).pipe(
        map(someResponse => {
          /* 
            SET IMG HERE
            user.img = someResponse
          */
          return user;
        }),
      )
    }

    return user$;
  }
}

In both scenarios, the factory handles API interactions. This approach leads to a clearer structure and enhances testability.

Answer 2

One way to improve the code is by following the principles of SOLID and dividing responsibilities effectively.

An entity called User has properties like name and img. It's recommended that the User entity does not have knowledge about the DBService.

To manage this, you can implement a factory that creates instances of User, where the factory itself is aware of the DBService. The factory could operate in two ways:

Create and provide a synchronous instance of User, then asynchronously fill the img property if needed by calling DbService.getSkin
Always create and return an asynchronous instance of User through an observable

The second option is preferred due to its more predictable behavior and avoids unexpected updates to the img property.

The revised code would look like this:

Case 1 - Return a `User` instance

interface User {
  name: string;
  img: ElementRef<HTMLCanvasElement> | string[];
}

@Injectable({providedIn: 'root')
export class UserFactory {
  constructor(private dbService: DBService) {}

  create(
    name: string,
    img?: ElementRef<HTMLCanvasElement> | string[],
  ): User {
    const user: User = {
      name,
      img,
    }

    if (!img) {
      this.dbService.getSkin(name).pipe(
        tap(someResponse => {
          /* 
            SET IMG HERE
            user.img = someResponse
          */
        }),
      ).subscribe();
    }

    return user;
  }
}

Case 2 - Return observable

interface User {
  name: string;
  img: ElementRef<HTMLCanvasElement> | string[];
}

@Injectable({providedIn: 'root')
export class UserFactory {
  constructor(private dbService: DBService) {}

  create(
    name: string,
    img?: ElementRef<HTMLCanvasElement> | string[],
  ): Observable<User> {
    const user: User = {
      name,
      img,
    }

    let user$: Observable<User> = of(user);

    if (!img) {
      user$ = this.dbService.getSkin(name).pipe(
        map(someResponse => {
          /* 
            SET IMG HERE
            user.img = someResponse
          */
          return user;
        }),
      )
    }

    return user$;
  }
}

In both scenarios, the factory handles API interactions. This approach leads to a clearer structure and enhances testability.

Answer 3

Answer №2

When setting up the constructor, make sure to initialize the service by passing it as an argument:

constructor(name: string,
        img?: ElementRef<HTMLCanvasElement> | string[], private imageService: ImageService) {
        
}

Afterwards, you can easily access your service by using:

this.imageService.getMethod()

Answer 4

When setting up the constructor, make sure to initialize the service by passing it as an argument:

constructor(name: string,
        img?: ElementRef<HTMLCanvasElement> | string[], private imageService: ImageService) {
        
}

Afterwards, you can easily access your service by using:

this.imageService.getMethod()

Answer 5

Answer №3

To simplify your code structure, consider creating a factory service that allows you to inject necessary services. This factory service can include a method called build, which takes the required parameters for creating a User object along with any additional services:

@Injectable({providedIn: 'root')
export class UserFactory {
  constructor(private _yourService: YourService) {}

  build(name: string, img?: ElementRef<HTMLCanvasElement> | string[]) {
    return new User(name, img, this._yourService);
  }
}

You can then utilize this factory service in the following manner:

@Component({...})
export class YourComponent {
  ...

  constructor(private _uFactory: UserFactory) {}

  ...

    const user = this._uFactory.buid(name, img);

  ...
}

Answer 6

To simplify your code structure, consider creating a factory service that allows you to inject necessary services. This factory service can include a method called build, which takes the required parameters for creating a User object along with any additional services:

@Injectable({providedIn: 'root')
export class UserFactory {
  constructor(private _yourService: YourService) {}

  build(name: string, img?: ElementRef<HTMLCanvasElement> | string[]) {
    return new User(name, img, this._yourService);
  }
}

You can then utilize this factory service in the following manner:

@Component({...})
export class YourComponent {
  ...

  constructor(private _uFactory: UserFactory) {}

  ...

    const user = this._uFactory.buid(name, img);

  ...
}

Angular: defining a new class instance and implementing various services

Answer №1

Case 1 - Return a `User` instance

Case 2 - Return observable

Answer №2

Answer №3

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Angular: defining a new class instance and implementing various services

Answer №1

Case 1 - Return a User instance

Case 2 - Return observable

Answer №2

Answer №3

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Case 1 - Return a `User` instance