Best practices for using this.i18n.t() vs I18nContext.current().t()

[vqhdev]

I'm looking at the code sample you provided in the documentation for : nestjs-i18n

import { Injectable } from '@nestjs/common';
import { I18nContext, I18nService } from 'nestjs-i18n';

@Injectable()
export class AppService {
  constructor(private readonly i18n: I18nService) {}

  getHello(): string {
    return this.i18n.t('test.HELLO', { lang: I18nContext.current().lang });
  }
}

I understand that both this.i18n.t() and I18nContext.current().t() are used to translate strings. However, I'm not sure why the code uses this.i18n.t('test.HELLO', { lang: I18nContext.current().lang }) instead of simply I18nContext.current().t('test.HELLO').

Could you please explain the difference between these two approaches and why the first one is preferred in this case?

[rubiin]

This is to add the language specific translation. Since you are doing the translation on service with i18nservice, it has no way of knowing the requested language and will always use the fallback if you don't add the { lang: I18nContext.current().lang } . e @vqhdev

[rubiin]

The first one is preferred on controller level as it does have request level access and so the context can resolve the language sent through headers, cookies, etc. Using this on service however will always fallback as service doesnt directly interact with request but only through controller.

[toonvanstrijp]

I think we've to make a V11. This version removes the I18nContext all together. I think it's working too vague and abstract now. We could better give the user control in how to deliver it to services/controllers etc.

[rubiin]

True. this.i18n.t('test.HELLO', { lang: I18nContext.current().lang }); this approach works good on both cpntroller and service. We can remove the translation method from I18nContext , that would be a breaking change though