How to pass parameters for dependency while Injecting services in services in Angular 2 ( Ionic 2 / Angular 2 / Typescript )

Question

I'm making a sample application to make connection to a websocket server in ionic 2 in typescript. link to repo

My requirement is to make the websocket connection during application start up

I'm using angular2-websocket to creating the connection.

References :

1. http://blog.thoughtram.io/angular/2015/09/17/resolve-service-dependencies-in-angular-2.html

2. http://blog.thoughtram.io/angular/2015/05/18/dependency-injection-in-angular-2.html

I'm getting a error " Cannot resolve all parameters for '$WebSocket'(String, Array, ?). Make sure that all the parameters are decorated with Inject or have valid type annotations and that '$WebSocket' is decorated with Injectable. "

CODE: app.ts

import {App, Platform} from 'ionic-framework/ionic';
import {TabsPage} from './pages/tabs/tabs';
import {ConnectionService} from './framework/connection/connection-service'
import {$WebSocket} from 'angular2-websocket/angular2-websocket';
import {bootstrap} from 'angular2/platform/browser';

// https://angular.io/docs/ts/latest/api/core/Type-interface.html
import {Type} from 'angular2/core';


@App({
  template: '<ion-nav [root]="rootPage"></ion-nav>',
  config: {}
})
export class MyApp {
  rootPage: Type = TabsPage;

  constructor(platform: Platform, private conn : ConnectionService) {
    platform.ready().then(() => {
      this.conn.connect();
    });
  }
}
bootstrap(MyApp, [$WebSocket, ConnectionService]);

connection-service.ts

import {Injectable, Component, Inject} from 'angular2/core';
import {$WebSocket} from 'angular2-websocket/angular2-websocket';
import {bootstrap} from 'angular2/platform/browser';

@Injectable()
export class ConnectionService {

    private _status: number;

    //private connection: $WebSocket;

    constructor( private connection : $WebSocket = new $WebSocket("ws://echo.websocket.org") ) {

    console.log("Starting connection");

   //this.connection = new $WebSocket("ws://echo.websocket.org");

    this.connection.onClose(this.onCloseHandler);
    this.connection.onError(this.onErrorHandler);
    this.connection.onOpen(this.onOpenHandler);
    this.connection.onMessage(this.onRecieveHandler, {});

}
...
public connect() {
    this.connection.connect(true);
}
...
}
bootstrap(ConnectionService, [$WebSocket]);

Answer 1

The Solution to my problem was using @App() Annotation's (Specific to ionic) provider field instead of using bootstrap

bootstrap(ConnectionService, 
    [provide($WebSocket, useValue: new WebSocket("ws://echo.websocket.org")]);

Eg.

@App({
  template: '<ion-nav [root]="rootPage"></ion-nav>',
  config: {},
  providers : [ provide( $WebSocket, { useValue: new $WebSocket("ws://echo.websocket.org") }), ConnectionService]
})

Working sample can be found here

Answer 2

Obviously the $WebSocket requires a string, array and another parameter which makes $WebSocket not injectable, at least not directly.

As a workaround you can use

import {Injectable, Component, Inject, provide} from 'angular2/core';

bootstrap(ConnectionService, 
    [provide( $WebSocket, { useValue: new $WebSocket("ws://echo.websocket.org") })]);

There are other options if the string literal is not what you want, like a factory.