Ngx-translate - TranslateHttpLoader with external URL


#1

I’m loading the translation files from the server using TranslateHttpLoader in my app.module.ts like this:

export function createTranslateLoader(http: Http) {
   return new TranslateHttpLoader(http, AppConfig.API_URL+'/static/i18n/', '.json');
}

@NgModule({
  ...
  
  imports: [

    TranslateModule.forRoot({
      loader: {
        provide: TranslateLoader,
        useFactory: (createTranslateLoader),
        deps: [Http]
      }
    }), 
    
  ],
  ...
})

Everything works fine, but i’m wondering if there is a way to catch event when the loader fails to retrieve the language file for whatever reason (server issues, net con etc.) and possibly load a local json file with some default translation strings?

I want to catch this event if the app on the first load fails to grab the language file , and fallback to minimal local json file to just display translated mainetnance page/error page or something.


#2

I would think this would require writing a custom loader.


#3

Before exporting createTranslateLoader(), make a request to the link (i.e. AppConfig.API_URL+’/static/i18n/).
If there is no response then Ionic will throw 404 Error. Trap this error using Custom Error Handling and point the value of AppConfig.API_URL to the local directory.


#4

@rapropos , @devX - thanks for pointing me the right direction guys, i wrote a custom loader that resolves the requirement:

import { Injectable } from '@angular/core';
import { Headers, Http, Response } from "@angular/http";
import { TranslateLoader } from '@ngx-translate/core';
import { AppConfig } from "./config"
import {Observable} from 'rxjs/Observable'; 
 

@Injectable()
export class CustomTranslateLoader implements TranslateLoader  {
    contentHeader = new Headers({"Content-Type": "application/json","Access-Control-Allow-Origin":"*"});

    constructor(private http: Http) {}
    getTranslation(lang: string): Observable<any>{
        var apiAddress = AppConfig.API_URL+"/static/i18n/"+ lang+".json";
        return Observable.create(observer => {
          this.http.get(apiAddress, { headers: this.contentHeader }).subscribe((res: Response) => {
                    observer.next(res.json());
                    observer.complete();               
                },
            error => {
                //  failed to retrieve from api, switch to local
                this.http.get("/assets/i18n/en.json").subscribe((res: Response) => {
                    observer.next(res.json());
                    observer.complete();               
                })
            }
            );
        }); 
    }
}

#5

Hi,

I felt on your solution and i really need to understand how you are doing that. Can you explain me with precision where to put that class and how/when to call it after for retrieving that translation from web URL ?

I don’t understand where to place it then where I should call it ?


#6
  • place the code above in your services folder as trans.loader.ts

  • in your app.module.ts:

import { TranslateModule, TranslateLoader } from '@ngx-translate/core';
import { CustomTranslateLoader } from '../services/trans.loader'

@NgModule({
  imports: [
    TranslateModule.forRoot({
      loader: {
        provide: TranslateLoader,
        useClass: CustomTranslateLoader,
        deps: [Http]
      }
    }),
  ]
})
  • then you can use TranslateService as usual, but your custom loader will be used instead of the default one