如何在提供者内部使用提供者

Question

I am using ionic2, which is Angular2, but this question is more Angular2 than Ionic framework. I have a provider such as this:

import {Injectable, Provider, Inject} from '@angular/core';
import {Http, Response, Headers} from '@angular/http';

@Injectable()
export class MyFirstProvider{

  constructor( @Inject(Http) http) {
      this.http = http;
  }
.
.
.

I have another provider such as this:

import {Injectable, Provider, Inject} from '@angular/core';
import {Http, Response, Headers} from '@angular/http';

@Injectable()
export class MySecondProvider{

  constructor( @Inject(Http) http) {
      this.http = http;
  }

  myCoolFunction(){
    console.log('I am one cool function'); 
  }
.
.
.

How can I use MySecondProvider's myCoolFunctions inside of MyFirstProvider?

Answer 1

By injecting it

@Injectable()
export class MyFirstProvider{

  constructor(private http:Http, 
      private mySecond: MySecondProvider) {}

  someMethod(){
    this.mySecond.myCoolFunctions();
  }
}

These classes are services, not providers. These services can and need to be registered as providers. A provider is a combination of key and value construction instruction. When DI looks up a type (key) it searches a components injector and its parent injectors until it finds one with a matching key and then returns its instance (the service).