multi-language-mixin.ts

export interface MultiLanguage {}

export type Constructor<T> = new(...args: any[]) => T;

export type MultiLanguageCtor = Constructor<MultiLanguage>;

export interface TranslationAvailable extends PipeTransform, OnDestroy {
  translate: TranslateService;
  cd: ChangeDetectorRef;
}

export function multiLanguageMixin<T extends Constructor<TranslationAvailable>>(base: T): MultiLanguageCtor & T {
  return class extends base implements PipeTransform, OnDestroy {
    private onLangChange?: Subscription;
    constructor(...args: any[]) { super(...args); }

    transform(value: any, ...args: any[]): any {
      if (!this.onLangChange) {
        this.onLangChange = this.translate.onLangChange.subscribe(() => this.cd.markForCheck());
      }

      return super.transform(value, ...args);
    }

    ngOnDestroy(): void {
      super.ngOnDestroy();
      this.onLangChange?.unsubscribe();
      this.onLangChange = undefined;
    }
  };
}