Aurelia navigation-view

navigation-view.js

import {
  inject, Container, ViewSlot, ViewLocator,
  customElement, noView, CompositionTransaction,
  CompositionEngine, bindable
} from 'aurelia-framework';

@noView()
@customElement('navigation-view')
@inject(Element, Container, ViewSlot, ViewLocator, CompositionEngine, CompositionTransaction)
export class NavigationView {
  @bindable viewModel;
  @bindable model;
  @bindable title;
  viewChanged = null;

  subscribers = [];
  stack = [];
  busy = false;

  constructor(element, container, viewSlot, viewLocator, compositionEngine, compositionTransaction) {
    this.element = element;
    this.container = container;
    this.viewSlot = viewSlot;
    this.viewLocator = viewLocator;
    this.compositionEngine = compositionEngine;
    this.compositionTransaction = compositionTransaction;
    this.controller = null;

    if (!('initialComposition' in compositionTransaction)) {
      compositionTransaction.initialComposition = true;
      this.compositionTransactionNotifier = compositionTransaction.enlist();
    }
  }

  get length() {
    return this.stack.length;
  }

  _getViewModel(instruction) {
    if (typeof instruction.viewModel === 'function') {
      instruction.viewModel = Origin.get(instruction.viewModel).moduleId;
    }

    if (typeof instruction.viewModel === 'string') {
      return this.compositionEngine.ensureViewModel(instruction);
    }

    return Promise.resolve(instruction);
  }

  created(owningView) {
    this.owningView = owningView;
  }

  bind(bindingContext, overrideContext) {
    this.container.viewModel = bindingContext;
    this.overrideContext = overrideContext;
  }

  attached() {
    this.navigate(this.viewModel, this.title, this.model);
  }

  _navigate(controller, title, swapDirection) {
    let oldController = this.controller;
    this.controller = controller;
    let classList = this.element.classList;
    this.title = title;

    let compositionHandler = () => {
      if (this.compositionTransactionNotifier) {
        this.compositionTransactionNotifier.done();
        this.compositionTransactionNotifier = null;
      }
      classList.remove(`nav-${swapDirection}`);
        this.busy = false;
    };

    if (!oldController) {
      return Promise.resolve(this.viewSlot.add(this.controller.view)).then( () => compositionHandler() );
    } else {
      classList.add(`nav-${swapDirection}`);

      this.invokeSubscribers(swapDirection);

      return Promise.all([
        this.viewSlot.add(this.controller.view),
        this.viewSlot.remove(oldController.view, true)
      ]).then( () => compositionHandler() );
    }
  }

  navigate(viewModel, title, model) {
    if (this.busy) return;

    this.busy = true;

    let childContainer = this.container.createChild();
    let instruction = {
      viewModel: viewModel,
      container: this.container,
      childContainer: childContainer,
      model: model,
      skipActivation: true
    };

    this._getViewModel(instruction).then(returnedInstruction => {
      this.invokeLifecycle(returnedInstruction.viewModel, 'canActivate', model).then(canActivate => {
        if (canActivate) {
          this.compositionEngine.createController(returnedInstruction).then(controller => {
            this.invokeLifecycle(returnedInstruction.viewModel, 'activate', model).then( () => {
              if (!this.compositionTransactionNotifier) {
                this.compositionTransactionOwnershipToken = this.compositionTransaction.tryCapture();
              }
              controller.automate(this.overrideContext, this.owningView);

              if (this.compositionTransactionOwnershipToken) {
                return this.compositionTransactionOwnershipToken.waitForCompositionComplete().then(() => {
                  this.compositionTransactionOwnershipToken = null;
                  if (this.controller !== null) {
                    this.stack.push({controller: this.controller, title: this.title});
                  }
                  this._navigate(controller, title, 'forward');
                });
              }
            });
          });
        }
      });
    });
  }

  navigateBack() {
    if (!this.busy && this.stack.length > 0) {
      this.busy = true;
      let previousState = this.stack.pop();
      let controller = previousState.controller;
      controller.bind(this);
      this._navigate(controller, previousState.title, 'back');
    }
  }

  subscribe(callback) {
    let subscribers = this.subscribers;

    subscribers.push(callback);

    return {
      dispose() {
        let idx = subscribers.indexOf(callback);
        if (idx !== -1) {
          subscribers.splice(idx, 1);
        }
      }
    };
  }

  invokeSubscribers(direction) {
    let i = this.subscribers.length;
    while (i--) {
      this.subscribers[i](direction);
    }
  }

  invokeLifecycle(instance, name, model) {
    if (typeof instance[name] === 'function') {
      let result = instance[name](model, this);

      if (result instanceof Promise) {
        return result;
      }

      if (result !== null && result !== undefined) {
        return Promise.resolve(result);
      }

      return Promise.resolve(true);
    }

    return Promise.resolve(true);
  }
}

The activate method of child viewModels are called passing the model as first argument and the NavigationView as second:

  activate(model, nav) {
    this.nav = nav;
  }

It can then be used to navigate to the following view from either the view or the viewModel:
nav.navigate('welcome', {title: 'test'})

Example animation:

/* animate page transitions */

.nav-forward div.page.au-enter-active {
  -webkit-animation: fadeInRight 1s;
  animation: fadeInRight 1s;
}
.nav-forward div.page.au-leave-active {
  -webkit-animation: fadeOutLeft 1s;
  animation: fadeOutLeft 1s;
}

.nav-back div.page.au-enter-active {
  -webkit-animation: fadeInLeft 1s;
  animation: fadeInLeft 1s;
}
.nav-back div.page.au-leave-active {
  -webkit-animation: fadeOutRight 1s;
  animation: fadeOutRight 1s;
}

Make the Navbar title animate when navigating:

<div class="center" ref="titleElement">${nav.title}</div>

.animate-title-forward-add {
  -webkit-animation: fadeInRight 1s;
  animation: fadeInRight 1s;
}

.animate-title-back-add {
  -webkit-animation: fadeInRight 1s;
  animation: fadeInLeft 1s;
}

  navChanged() {
    this.subscription = this.nav.subscribe((direction) => {
      return this.cssAnimator.animate(this.titleElement, `animate-title-${direction}`);
    });
  }

  detached() {
    if (this.subscription) this.subscription.dispose();
  }