Angular 2 Global Constants Provider Injector Method

Question

I have a global constants like root directory that I want every component to have access to. In another stackoverflow question the answer was to create a constants class and imp

Answer 1

import {Component} from 'angular2/core'
import { Constants } from './constants'

@Component({
    selector: 'test',
    template: `  
                    Constants: {{ urlTemplate }}

              `
    providers:[Constants]

})

export class AppComponent{

  constructor(constants: Constants){
    this.urlTemplate = constants.root_dir;
  }

}

You can use adding Constants in providers:[Constants]

---

The decorator @Injectable It is not necessary in this case, but Google recommends always use You can see here: https://angular.io/docs/ts/latest/guide/dependency-injection.html#!#why-injectable-

---

/*
We recommend adding @Injectable() to every service class, even those that don't have dependencies and, therefore, do not technically require it. Here's why:
Future proofing: No need to remember @Injectable when we add a dependency later.
Consistency: All services follow the same rules, and we don't have to wonder why a decorator is missing
*/

//@Injectable() 
export class Constants{
  root_dir: string;

  constructor(){
      this.root_dir = 'http://google.com/'
    }
  }

Plunker

---

About @Inject used, you can read something here: what is the difference between using (@Inject(Http) http: Http) or not

---

Now if you want this globally can add in bootstrap

//main entry point
import {bootstrap} from 'angular2/platform/browser';
import {AppComponent} from './app';
import { Constants } from './constants';


bootstrap(AppComponent, Constants)
  .catch(err => console.error(err));

---

//import { Injectable } from 'angular2/core'

//@Injectable()
export class Constants{
root_dir: string;

  constructor(){
      this.root_dir = 'http://google.com/'
    }
  }

---

import {Component, Inject} from 'angular2/core'
import { Constants } from './constants';

@Component({
    selector: 'test',
    template: `  
                    Constants: {{ urlTemplate }}

              `

})


export class AppComponent{

  constructor(@Inject (Constants) constants: Constants){
    this.urlTemplate = constants.root_dir;
  }

}

Plunker