Function ɵɵconditional

packages/core/src/render3/instructions/control_flow.ts:163–219

(matchingTemplateIndex: number, contextValue?: T)

 * @codeGenApi
 */
export function ɵɵconditional<T>(matchingTemplateIndex: number, contextValue?: T) {
  performanceMarkFeature('NgControlFlow');

  const hostLView = getLView();
  const bindingIndex = nextBindingIndex();
  const prevMatchingTemplateIndex: number =
    hostLView[bindingIndex] !== NO_CHANGE ? hostLView[bindingIndex] : -1;
  const prevContainer =
    prevMatchingTemplateIndex !== -1
      ? getLContainer(hostLView, HEADER_OFFSET + prevMatchingTemplateIndex)
      : undefined;
  const viewInContainerIdx = 0;

  if (bindingUpdated(hostLView, bindingIndex, matchingTemplateIndex)) {
    const prevConsumer = setActiveConsumer(null);
    try {
      // The index of the view to show changed - remove the previously displayed one
      // (it is a noop if there are no active views in a container).
      if (prevContainer !== undefined) {
        removeLViewFromLContainer(prevContainer, viewInContainerIdx);
      }

      // Index -1 is a special case where none of the conditions evaluates to
      // a truthy value and as the consequence we've got no view to show.
      if (matchingTemplateIndex !== -1) {
        const nextLContainerIndex = HEADER_OFFSET + matchingTemplateIndex;
        const nextContainer = getLContainer(hostLView, nextLContainerIndex);
        const templateTNode = getExistingTNode(hostLView[TVIEW], nextLContainerIndex);

        const dehydratedView = findAndReconcileMatchingDehydratedViews(
          nextContainer,
          templateTNode,
          hostLView,
        );
        const embeddedLView = createAndRenderEmbeddedLView(hostLView, templateTNode, contextValue, {
          dehydratedView,
        });

        addLViewToLContainer(
          nextContainer,
          embeddedLView,
          viewInContainerIdx,
          shouldAddViewToDom(templateTNode, dehydratedView),
        );
      }
    } finally {
      setActiveConsumer(prevConsumer);
    }
  } else if (prevContainer !== undefined) {
    // We might keep displaying the same template but the actual value of the expression could have
    // changed - re-bind in context.
    const lView = getLViewFromLContainer<T | undefined>(prevContainer, viewInContainerIdx);
    if (lView !== undefined) {
      lView[CONTEXT] = contextValue;
    }
  }
}