CODEWITHSUNDEEP
angulardependency-injection
BeetleJuice
BeetleJuice

Reputation: 40916

Angular InjectionToken; what is 'app.config'?

I am following the docs on how to provide, then inject a non-class instance; specifically I want to provide application wide constants. The docs use the InjectionToken for this, but the explanations are very bare; consider the first part:

app.config.ts

import { InjectionToken } from '@angular/core';

export let APP_CONFIG = new InjectionToken<AppConfig>('app.config');

What's the point of the 'app.config' string? Every example of InjectorToken that I see here uses that, but none discusses what it means or refers to.

Upvotes: 4

Views: 2130

Answers (1)

Max Koretskyi
Max Koretskyi

Reputation: 105517

It's a description as can be seen from the parameter name:

export class InjectionToken<T> extends OpaqueToken {
  constructor(desc: string) { super(desc); }
              ^^^^

  toString(): string { return `InjectionToken ${this._desc}`; }
}

It can be used for debugging purposes as it's seen in the toString method.

It is probably modeled after Symbol which also receives description string in the constructor:

Parameters

  • description - Optional Optional, string. A description of the symbol which can be used for debugging but not to access the symbol itself.

Refer to the Angular 2 OpaqueToken vs Angular 4 InjectionToken to understand why the InjectionToken was introduced.

Upvotes: 2

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