Angular InjectionToken; what is 'app.config'?

Question

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.

score 2 · Accepted Answer · answered Jul 04 '17 at 04:34

2

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.

answered Jul 04 '17 at 04:34

Max Koretskyi

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I am struggling to understand. does that mean, we should keep `'app.config'` unique across the app ? – Shashank Vivek Jan 06 '18 at 16:29
what is `app.config` you're asking about? – Max Koretskyi Jan 06 '18 at 16:48
I mean `export let APP_CONFIG = new InjectionToken('app.config');` . The param. – Shashank Vivek Jan 06 '18 at 18:00
@ShashankVivek, it's better if you ask a separate question – Max Koretskyi Jan 06 '18 at 18:45

Angular InjectionToken; what is 'app.config'?

1 Answers1