Exploring how to utilize class properties within Angular templates

Question

Exploring how to utilize class properties within Angular templates

I am facing an issue with using a template property in Angular. Despite my attempts, it is not functioning as expected and I am unable to pinpoint the cause of the problem. To illustrate, I have set up a demonstration here:

https://github.com/Fulkerson/angular-property

This example is based on the Tour of Heroes. In my recent commit, I introduced the property propname which simply returns the value of name. Subsequently, I attempted to utilize this property in the dashboard (main page).

Essentially, my objective is to incorporate multiple properties that manipulate a field differently. However, why am I encountering difficulties in utilizing these properties within templates? Is there an alternative approach to achieve the desired outcome?

angular typescript

Answer 1

Answer №1

When you utilize the heroService.getHeroes method, the data returned is a plain JSON object rather than utilizing the defined getter in the Hero class. To make use of the getter from the class, it is necessary to return an Array containing actual instances of Hero.

1/ For simplicity, we have included a constructor for the Hero class in app/hero.ts

  constructor ({id,name} = {id: undefined, name: undefined}) {
    this.id = id;
    this.name = name;
  }

2/ Instead of returning basic js data from heroService, we perform a mapping to generate an array of Hero instances in dashboard.component.ts

getHeroes(): void {
    this.heroService.getHeroes()
      .subscribe(heroes => 
        this.heroes = heroes
        .slice(1, 5)
        .map(hero => new Hero(hero))
      );
  }

And there you have it!

A stackblitz based on your github repository can be found here

Answer 2

When you utilize the heroService.getHeroes method, the data returned is a plain JSON object rather than utilizing the defined getter in the Hero class. To make use of the getter from the class, it is necessary to return an Array containing actual instances of Hero.

1/ For simplicity, we have included a constructor for the Hero class in app/hero.ts

  constructor ({id,name} = {id: undefined, name: undefined}) {
    this.id = id;
    this.name = name;
  }

2/ Instead of returning basic js data from heroService, we perform a mapping to generate an array of Hero instances in dashboard.component.ts

getHeroes(): void {
    this.heroService.getHeroes()
      .subscribe(heroes => 
        this.heroes = heroes
        .slice(1, 5)
        .map(hero => new Hero(hero))
      );
  }

And there you have it!

A stackblitz based on your github repository can be found here

Answer 3

Answer №2

Well, it seems like the issue you're facing is due to adding a new getter to the Hero class while displaying heroes from a mocked data service in the dashboard. The data being used is just a simple array of objects defined in in-memory-data.service.ts:

const heroes = [
      { id: 11, name: 'Mr. Nice' },
      { id: 12, name: 'Narco' },
      { id: 13, name: 'Bombasto' },
      { id: 14, name: 'Celeritas' },
      { id: 15, name: 'Magneta' },
      { id: 16, name: 'RubberMan' },
      { id: 17, name: 'Dynama' },
      { id: 18, name: 'Dr IQ' },
      { id: 19, name: 'Magma' },
      { id: 20, name: 'Tornado' }
    ];

In the original example, this wasn't an issue as the Hero class was more of an interface or type annotation. However, since you've added methods to that class, they don't exist within the array of objects.

So essentially, your template is trying to access a propname property from these items in the array, which is currently returning undefined. As a result, the names aren't being displayed on the page. To fix this, you can modify the array definition like so:

const heroes = [
      Object.assign(new Hero(), { id: 11, name: 'Mr. Nice' }),
      ...
    ];

(Alternatively, you could give Hero a constructor with parameters and utilize that instead of Object.assign). This way, you'll have an array of actual Hero objects.

Answer 4

Well, it seems like the issue you're facing is due to adding a new getter to the Hero class while displaying heroes from a mocked data service in the dashboard. The data being used is just a simple array of objects defined in in-memory-data.service.ts:

const heroes = [
      { id: 11, name: 'Mr. Nice' },
      { id: 12, name: 'Narco' },
      { id: 13, name: 'Bombasto' },
      { id: 14, name: 'Celeritas' },
      { id: 15, name: 'Magneta' },
      { id: 16, name: 'RubberMan' },
      { id: 17, name: 'Dynama' },
      { id: 18, name: 'Dr IQ' },
      { id: 19, name: 'Magma' },
      { id: 20, name: 'Tornado' }
    ];

In the original example, this wasn't an issue as the Hero class was more of an interface or type annotation. However, since you've added methods to that class, they don't exist within the array of objects.

So essentially, your template is trying to access a propname property from these items in the array, which is currently returning undefined. As a result, the names aren't being displayed on the page. To fix this, you can modify the array definition like so:

const heroes = [
      Object.assign(new Hero(), { id: 11, name: 'Mr. Nice' }),
      ...
    ];

(Alternatively, you could give Hero a constructor with parameters and utilize that instead of Object.assign). This way, you'll have an array of actual Hero objects.

Exploring how to utilize class properties within Angular templates

Answer №1

Answer №2

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