ng2-translate not working in lazy-loaded module

Question

I'm using ng2-translate for language handling in an Angular 2 RC5 app I'm creating. The app has two feature modules, one lazy loaded and one eager loaded. TranslateModule is made available through a shared module. The problem is that the translate pipe works fine in the eager-loaded module but not the lazy-loaded one. To verify it has to do with the loading method I converted both to eager-loading and everything worked fine.

A plunk that demonstrates the issue can be found here: Plunker The significant code is below as well.

The initial page is the eager-loaded one, hence why the strings look fine. Click Login and it will go to the lazy-loaded one where all strings are upper-case, i.e. not translated.

Any help would be appreciated.

app.module:

import { NgModule }      from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { TranslateModule } from 'ng2-translate/ng2-translate';
import { AppComponent }  from './app.component';
import { WelcomeModule } from './welcome/welcome.module';
import { routing }       from './app.routing';

@NgModule({
  imports: [ BrowserModule, WelcomeModule, TranslateModule.forRoot(), routing ],
  declarations: [ AppComponent ],
  bootstrap: [ AppComponent ]
})
export class AppModule { }

app.routing:

import { Routes, RouterModule } from '@angular/router';

export const routes: Routes = [
  { path: '', redirectTo: 'welcome', pathMatch: 'full'},
  { path: 'backend', loadChildren: 'app/backend/backend.module' }
];

export const routing = RouterModule.forRoot(routes);

app.component:

import { Component } from '@angular/core';
import { TranslateService } from 'ng2-translate/ng2-translate';

@Component({
    selector: 'my-app',
    template: `
        <router-outlet></router-outlet>
    `
})
export class AppComponent { 
    constructor(translate: TranslateService) {
        // this language will be used as a fallback when a translation isn't found in the current language
        translate.setDefaultLang('en');

        // the lang to use, if the lang isn't available, it will use the current loader to get them
        translate.use('en');
    }
}

shared.module:

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { HttpModule } from '@angular/http';
import { TranslateModule } from 'ng2-translate/ng2-translate';

@NgModule({
    imports: [
        CommonModule,
        HttpModule,
        TranslateModule.forRoot()
    ],
    exports: [
        CommonModule,
        TranslateModule
    ],

})
export class SharedModule {}

welcome.module (eager loaded)

import { NgModule }      from '@angular/core';
import { SharedModule } from '../shared/shared.module';
import { WelcomeComponent }  from './welcome.component';
import { routing } from './welcome.routing';

@NgModule({
  imports: [ SharedModule, routing ],
  declarations: [ WelcomeComponent ]
})
export class WelcomeModule { }

welcome.component:

import { Component } from '@angular/core';

@Component({
    template: `
        <h2>{{ 'PLEASELOGIN' | translate }}</h2>
        <nav><a routerLink="/backend">{{ 'LOGIN' | translate }}</a></nav>
    `
})
export class WelcomeComponent { }

welcome.routing

import { RouterModule }  from '@angular/router';

import { WelcomeComponent } from './welcome.component';

export const routing = RouterModule.forChild([
    { path: 'welcome', component: WelcomeComponent}
]);

backend.module (lazy loaded)

import { NgModule } from '@angular/core';
import { SharedModule } from '../shared/shared.module';
import { BackendComponent } from './backend.component';
import { routing } from './backend.routing';

@NgModule({
    imports: [ SharedModule, routing ],
    declarations: [ BackendComponent ]
})
export default class BackendModule { }

backend.component:

import { Component } from '@angular/core';

@Component({
    template: `
        <h2>{{ 'WELCOME' | translate }}</h2>
        <nav><a routerLink="/welcome">{{ 'LOGOUT' | translate }}</a></nav>
    `
})
export class BackendComponent { }

backend.routing

import { Routes, RouterModule }  from '@angular/router';
import { BackendComponent }    from './backend.component';

const routes: Routes = [
    { path: '', component: BackendComponent }
];

export const routing = RouterModule.forChild(routes);

en.json

{
    "LOGIN": "Login",
    "LOGOUT": "Logout",
    "WELCOME": "Welcome!",
    "PLEASELOGIN": "Please Login"
}

Answer 1

I had the same problem. Adding TranslateLoader and TranslateService to the forRoot method solved the problem.

    import {TranslateModule, TranslateService, TranslateLoader, TranslateStaticLoader} from 'ng2-translate/ng2-translate';
    @NgModule({
        imports: [..,TranslateModule],
        declarations: [..],
        exports: [ .., TranslateModule]
    })
    export class SharedModule {

    static forRoot(): ModuleWithProviders {

       function translateLoader(http: Http) {
            return new TranslateStaticLoader(http, 'i18n', '.json');
        }
        return {
            ngModule: SharedModule,
            providers: [UserService, ItemService, {
                provide: TranslateLoader,
                useFactory: translateLoader,
                deps: [Http]
            },
                TranslateService],
        };
    }
    }

Answer 2

Though the accepted answer pointed me in the right direction, the translator was not working in the lazy loaded module. In other modules it was working.

I had to inject the TranslatorService again in the lazy loaded module's main component and init the language settings like I've done in app.component.ts

export class MainComponentOfLazyLoadedModule implements OnInit {

    constructor(private translate: TranslateService) {
        Language.currentLang = "en";
        translate.addLangs(["en", "sp"]);
        translate.setDefaultLang(Language.currentLang);
        translate.use(Language.currentLang);
    }

    ngOnInit() {

    }

}