Function templateHandling

libs/cdk/template/src/lib/utils.ts:50–106

(
  viewContainerRef: ViewContainerRef
)

 *
 */
export function templateHandling<N, C>(
  viewContainerRef: ViewContainerRef
): {
  add(name: N, templateRef: TemplateRef<C>): void;
  get(name: N): TemplateRef<C>;
  get$(name: N): Observable<TemplateRef<C>>;
  createEmbeddedView(name: N, context?: C, index?: number): EmbeddedViewRef<C>;
} {
  const templateCache = new Map<N, Subject<TemplateRef<C>>>();

  const get$ = (name: N): Observable<TemplateRef<C>> => {
    return templateCache.get(name) || of(undefined);
  };
  const get = (name: N): TemplateRef<C> | undefined => {
    let ref: TemplateRef<C>;
    const templatRef$ = get$(name);
    if (templatRef$) {
      const sub = templatRef$.subscribe((r) => (ref = r));
      sub.unsubscribe();
    }
    return ref;
  };

  return {
    add(name: N, templateRef: TemplateRef<C>): void {
      assertTemplate(name, templateRef);
      if (!templateCache.has(name)) {
        templateCache.set(
          name,
          new BehaviorSubject<TemplateRef<C>>(templateRef)
        );
      } else {
        templateCache.get(name).next(templateRef);
      }
    },
    get$,
    get,
    createEmbeddedView: (name: N, context?: C) =>
      createEmbeddedView(viewContainerRef, get(name), context),
  };

  //
  function assertTemplate<T>(
    property: any,
    templateRef: TemplateRef<T> | null
  ): templateRef is TemplateRef<T> {
    const isTemplateRefOrNull = !!(
      !templateRef || templateRef.createEmbeddedView
    );
    if (!isTemplateRefOrNull) {
      throw new Error(
        `${property} must be a TemplateRef, but received ${typeof templateRef}`
      );
    }
    return isTemplateRefOrNull;
  }
}