Method postViewInit

core/src/components/nav/nav.tsx:789–865

* Adds and Removes the views from the navigation stack. * * @param enteringView The view being entered. * @param leavingView The view being left. * @param ti The instructions.

(
    enteringView: ViewController | undefined,
    leavingView: ViewController | undefined,
    ti: TransitionInstruction
  )

   * @param ti The instructions.
   */
  private postViewInit(
    enteringView: ViewController | undefined,
    leavingView: ViewController | undefined,
    ti: TransitionInstruction
  ): void {
    assert(leavingView || enteringView, 'Both leavingView and enteringView are null');
    assert(ti.resolve, 'resolve must be valid');
    assert(ti.reject, 'reject must be valid');

    // Compute the views to remove.
    const opts = ti.opts!;
    const { insertViews, removeStart, removeCount } = ti;
    /** Records the view to destroy */
    let destroyQueue: ViewController[] | undefined;

    // there are views to remove
    if (removeStart !== undefined && removeCount !== undefined) {
      assert(removeStart >= 0, 'removeStart can not be negative');
      assert(removeCount >= 0, 'removeCount can not be negative');

      destroyQueue = [];
      for (let i = removeStart; i < removeStart + removeCount; i++) {
        const view = this.views[i];
        if (view !== undefined && view !== enteringView && view !== leavingView) {
          destroyQueue.push(view);
        }
      }
      // default the direction to "back"
      opts.direction ??= 'back';
    }

    const finalNumViews = this.views.length + (insertViews?.length ?? 0) - (removeCount ?? 0);
    assert(finalNumViews >= 0, 'final balance can not be negative');
    if (finalNumViews === 0) {
      printIonWarning(
        `[ion-nav] - You can't remove all the pages in the navigation stack. nav.pop() is probably called too many times.`,
        this,
        this.el
      );

      throw new Error('navigation stack needs at least one root page');
    }

    // At this point the transition can not be rejected, any throw should be an error
    // Insert the new views in the stack.
    if (insertViews) {
      // add the views to the
      let insertIndex = ti.insertStart!;
      for (const view of insertViews) {
        this.insertViewAt(view, insertIndex);
        insertIndex++;
      }

      if (ti.enteringRequiresTransition) {
        // default to forward if not already set
        opts.direction ??= 'forward';
      }
    }