Method prepareTI

core/src/components/nav/nav.tsx:688–746

(ti: TransitionInstruction)

  }

  private prepareTI(ti: TransitionInstruction) {
    const viewsLength = this.views.length;

    ti.opts ??= {};
    ti.opts.delegate ??= this.delegate;

    if (ti.removeView !== undefined) {
      assert(ti.removeStart !== undefined, 'removeView needs removeStart');
      assert(ti.removeCount !== undefined, 'removeView needs removeCount');

      const index = this.views.indexOf(ti.removeView);
      if (index < 0) {
        throw new Error('removeView was not found');
      }
      ti.removeStart! += index;
    }
    if (ti.removeStart !== undefined) {
      if (ti.removeStart < 0) {
        ti.removeStart = viewsLength - 1;
      }
      if (ti.removeCount! < 0) {
        ti.removeCount = viewsLength - ti.removeStart;
      }
      ti.leavingRequiresTransition = ti.removeCount! > 0 && ti.removeStart + ti.removeCount! === viewsLength;
    }

    if (ti.insertViews) {
      // allow -1 to be passed in to auto push it on the end
      // and clean up the index if it's larger then the size of the stack
      if (ti.insertStart! < 0 || ti.insertStart! > viewsLength) {
        ti.insertStart = viewsLength;
      }
      ti.enteringRequiresTransition = ti.insertStart === viewsLength;
    }

    const insertViews = ti.insertViews;
    if (!insertViews) {
      return;
    }
    assert(insertViews.length > 0, 'length can not be zero');
    const viewControllers = convertToViews(insertViews);

    if (viewControllers.length === 0) {
      throw new Error('invalid views to insert');
    }

    // Check all the inserted view are correct
    for (const view of viewControllers) {
      view.delegate = ti.opts.delegate;
      const nav = view.nav;
      if (nav && nav !== this) {
        throw new Error('inserted view was already inserted');
      }
      if (view.state === VIEW_STATE_DESTROYED) {
        throw new Error('inserted view was already destroyed');
      }
    }
    ti.insertViews = viewControllers;