Utilizing Dependency Injection with Angular 2, Ionic 2, and TypeScript

I'm currently facing issues with bootstrapping certain files in my application. Specifically, I am working on extending the Ionic2 tabs example.

Within my codebase, I have a Service and a User file, both annotated with @injectable. I am aiming for a single instance throughout the entire app, so my approach revolves around bootstrapping it. I have included Platform in the providers, but I am uncertain whether I should have one instance for the entire app or per component?

import {App, Platform} from 'ionic-angular';
import {bootstrap} from 'angular2/platform/browser';
import {TabsPage} from './pages/tabs/tabs';
import {User} from './User.ts';
import {Service} from './Service.ts';
import {Type} from 'angular2/core';

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

    rootPage: Type = TabsPage;

    constructor(platform: Platform, user: User) {

        platform.ready().then(() => {
            user.start();
        });

    }
}

bootstrap(MyApp, [
    Service,
    User 
]);

Upon inspection, I noticed two errors appearing in the console

Cannot resolve all parameters for 'Platform'(?). Make sure that all the parameters are decorated with Inject or have valid type annotations and that 'Platform' is decorated with Injectable.

followed by

Uncaught TypeError: Cannot read property 'getOptional' of undefined

As an illustration, here is an excerpt from my service

import {Injectable} from 'angular2/core';

@Injectable()
export class Service {
   //
}

Answer №1

Tips for Injecting Services with Parameters in Angular 2 (Ionic 2 / Angular 2 / Typescript)

According to this post, the @App decorator in Ionic bootstraps the app. By adding User and Service to the providers, everything is working smoothly. It is noted that Platform does not need to be included in the providers array.

@App({
    template: '<ion-nav [root]="rootPage"></ion-nav>',
    providers: [User, Service]
})

Answer №2

When defining providers for your component, there is no requirement to mention the Platform specifically:

@App({
  template: '<ion-nav [root]="rootPage"></ion-nav>'
  providers: [Platform] // <------
})
export class MyApp {

  rootPage: Type = TabsPage;

  constructor(platform: Platform, user: User) {
    (...)
  }
}

Furthermore, the inclusion of the .ts extension in your imports may not be necessary:

//import {User} from './User.ts';
//import {Service} from './Service.ts';
import {User} from './User';
import {Service} from './Service';

Are you implementing TypeScript or ES6 in your project?

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