Ember Infinity

Demo: @eflexsystems/ember-infinity.github.io/@eflexsystems/ember-infinity/

Simple, flexible infinite scrolling for Ember CLI Apps. Works out of the box with the Kaminari Gem.

Table of Contents:

• Installation
• Basic Usage
• Service Methods
• Non Blocking Model Hook
• Advanced Usage
• Model Event Hooks
• Custom Store
• Infinity Loader
• Load Previous Pages
• Ember Concurrency Usage
• Testing

Also:

Installation

ember install @eflexsystems/ember-infinity

As of v2.0.0, we support Node 10 and above. We test against ember-source > 3.8. Try out v2.0.0. If it doesn't work or you don't have the right polyfills because you are on an older Ember version, then v1.4.9 will be your best bet.

Basic Usage

@eflexsystems/ember-infinity exposes 3 consumable items for your application.

1. infinity service

2. infinity-loader component

3. Route Mixin (deprecated and removed as of 1.1). If you still want to upgrade, but keep your Route mixins, install 1.0.2. See old docs (here)[https://github.com/@eflexsystems/ember-infinity/@eflexsystems/ember-infinity/blob/2e0cb02e5845a97cad8783893cd7f4ddcf5dc5a7/README.md]

Service Component Approach

Ember Infinity is based on a component-service approach wherein your application is viewed as an interaction between your components (ephemeral state) and service (long term state).

As a result, we can intelligently store your model state to provide you the ability to cache and invalidate your cache when you need to. If you provide an optional infinityCache timestamp (in ms), the infinity service model hook will return the existing collection (and not make a network request) if the timestamp has not yet expired. Be careful as this will also circumvent your ability to receive fresh data on every route visit.

Moreover, you are not restricted to only fetching items in the route. Fetch away in any top-level component!

Let's see how simple it is to fetch a list of products. Instead of this.store.query('product') or this.store.findAll('product'), you simply invoke this.infinity.model('product') and under the hood, @eflexsystems/ember-infinity will query the store and manage fetching new records for you!

import Route from '@ember/routing/route';
import { inject as service } from '@ember/service';

export default class InfinityRoute extends Route {
  @service infinity

  model() {
    return this.infinity.model('product');
  }
}

{{#each model as |product|}}
  <h1>{{product.name}}</h1>
  <h2>{{product.description}}</h2>
{{/each}}

<InfinityLoader @infinityModel={{model}} />

Whenever the infinity-loader component is in view, we will fetch the next page for you.

Response Meta Expectations

By default, @eflexsystems/ember-infinity expects the server response to contain something about how many total pages it can expect to fetch. @eflexsystems/ember-infinity defaults to looking for something like meta: { total_pages: 20 } in your response. See Advanced Usage.

Multiple Infinity Models in one Route

Let's look at a more complicated example using multiple infinity models in a route. Super easy!

import Route from '@ember/routing/route';
import RSVP from 'rsvp';
import { inject as service } from '@ember/service';

export default class InfinityRoute extends Route {
  @service infinity;

  model() {
    return RSVP.hash({
      products: this.infinity.model('product'),
      users: this.infinity.model('user')
    });
  }
}

{{!-- templates/products.hbs --}}

<aside>
  {{#each model.users as |user|}}
    <h1>{{user.username}}</h1>
  {{/each}}

  <InfinityLoader @infinityModel={{model.users}} />
</aside>

<section>
  {{#each model.products as |product|}}
    <h1>{{product.name}}</h1>
    <h2>{{product.description}}</h2>
  {{/each}}

  <InfinityLoader @infinityModel={{model.products}} />
<section>

Service Methods

The infinity service also exposes 5 methods to fetch & mutate your collection:

1. model
2. replace
3. flush
4. pushObjects
5. unshiftObjects

The model hook will fetch the first page you request and pass the result to your template.

import Route from '@ember/routing/route';
import { inject as service } from '@ember/service';

export default class ProductsRoute extends Route {
  @service infinity;

  model() {
    return this.infinity.model('product');
  }
}

Moreover, if you want to intelligently cache your infinity model, pass { infinityCache: timestamp } and we will return the cached collection if the future timestamp is less than the current time (in ms) if your users revisit the same route.

import Route from '@ember/routing/route';
import { inject as service } from '@ember/service';

export default class ProductsRoute extends Route {
  @service infinity;

  model() {
    return this.infinity.model('product', { infinityCache: 36000 }); // timestamp expiry of 10 minutes (in ms)
  }
}

Let's see an example of using replace.

import Controller from '@ember/routing/route';
import { inject as service } from '@ember/service';

export default class Products extends Route {
  @service infinity;

  actions: {
    /**
      @method filterProducts
      @param {String} query
    */
    async filterProducts(query) {
      let products = await this.store.query('product', { query });
      // model is the collection returned from the route model hook
      this.infinity.replace(get(this, 'model'), products);
    }
  }
}

import Route from '@ember/routing/route';
import { inject as service } from '@ember/service';

export default class ProductsRoute extends Route {
  @service infinity

  model() {
    return this.infinity.model('product');
  }
}

<input type="search" placeholder="Search Products" oninput={{action "filterProducts"}} />

{{#each model as |product|}}
  <h1>{{product.name}}</h1>
  <h2>{{product.description}}</h2>
{{/each}}

<InfinityLoader @infinityModel={{model.products}} />

Closure Actions

If you want to use closure actions with @eflexsystems/ember-infinity and the infinity-loader component, you need to be a little bit more explicit. Generally you should let the infinity service handle fetching records for you, but if you have a special case, this is how you would do it:

See the Ember docs on passing actions to components here.

import Controller from '@ember/routing/route';
import { inject as service } from '@ember/service';
import { action } from '@ember/object';

export default class ProductsController extends Controller {
  @service infinity

  /**
    Note this must be handled by you.  An action will be called with the result of your Route model hook from the `infinity-loader` component, similar to this:
    // closure action in infinity-loader component
    get(this, 'infinityLoad')(infinityModelContent);

    @method loadMoreProduct
    @param {InfinityModel} products
  */
  @action
  loadMoreProduct(products) {
    // Perform other logic ....
    this.infinity.infinityLoad(products);
  }
}

import Route from '@ember/routing/route';
import { inject as service } from '@ember/service';

export default class ProductsRoute extends Route {
  @service infinity

  model() {
    return this.infinity.model('product');
  }
}

{{!-- some nested component in your template file where action bubbling does not reach your route --}}
{{#each model as |product|}}
  <h1>{{product.name}}</h1>
  <h2>{{product.description}}</h2>
{{/each}}

{{infinity-loader infinityModel=model infinityLoad=(action "loadMoreProduct")}}

Non-Blocking Model Hook

In the world of optimistic route transitions & skeleton UI, it's necessary to return a POJO or similar primitive to Ember's Route#model hook to ensure the transition is not blocked by promise.

model() {
  return {
    posts: this.infinity.model('post')
  };
}

Advanced Usage

JSON Request/Response Customization

By default, @eflexsystems/ember-infinity will send pagination parameters as part of a GET request as follows

/items?per_page=5&page=1

and will expect to receive metadata in the response payload via a total_pages param in a meta object

{
  items: [
    {id: 1, name: 'Test'},
    {id: 2, name: 'Test 2'}
  ],
  meta: {
    total_pages: 3
  }
}

If you wish to customize some aspects of the JSON contract for pagination, you may do so via your model hook. For example, you may want to customize the following:

Default:

• perPageParam: per_page,
• pageParam: page,
• totalPagesParam: meta.total_pages,
• countParam: meta.count,

Example Customization shown below:

• perPageParam: per,
• pageParam: pg,
• totalPagesParam: meta.total,
• countParam: meta.records,

import Route from '@ember/routing/route';
import { inject as service } from '@ember/service';

export default class ProductsRoute extends Route {
  @service infinity

  model() {
    /* Load pages of the Product Model, starting from page 1, in groups of 12. Also set query params by handing off to infinityModel */
    return this.infinity.model('product', { perPage: 12, startingPage: 1,
      perPageParam: 'per', pageParam: 'pg', totalPagesParam: 'meta.total', countParam: 'meta.records' });
  }
}

This will result in request query params being sent out as follows

/items?per=5&pg=1

and @eflexsystems/ember-infinity will be set up to parse the total number of pages from a JSON response like this:

{
  items: [
    ...
  ],
  meta: {
    total: 3
  }
}

You can also prevent the per_page or page parameters from being sent by setting perPageParam or pageParam to null, respectively. Moreover, if your backend passes the total number of records instead of total pages, then as it's replacement, set the countParam.

Lastly, if you need some global configuration for these params, setup an extended infinity model to import in each of your routes.

Example JSON-API customization

import Route from '@ember/routing/route';
import { inject } from '@ember/service';

export default class ProductsRoute extends Route {
  @service infinity

  model() {
    return this.infinity.model('product', {
      perPage: 20,
      startingPage: 1,
      perPageParam: 'page[size]',
      pageParam: 'page[number]'
    });
  },
}

Cursor-based pagination

If you are serving a continuously updating stream, it's helpful to keep track of your place in the list while paginating to avoid duplicates. This is known as cursor-based pagination and is common in popular APIs like Twitter, Facebook, and Instagram. Instead of relying on page_number to paginate, you'll want to extract the min_id or min_updated_at from each page of results, so that you can fetch the next page without risking duplicates if new items are added to the top of the list by other users in between requests.

To do this, implement the afterInfinityModel hook as follows:

import Route from '@ember/routing/route';
import InfinityModel from '@eflexsystems/ember-infinity/lib/infinity-model';

const ExtendedInfinityModel = InfinityModel.extend({
  buildParams() {
    let params = this._super(...arguments);
    params['min_id']: get(this, '_minId'); // where `this` is the infinityModel instance
    params['min_updated_at']: get(this, '_minUpdatedAt');
    return params;
  },
  afterInfinityModel(posts) {
    let loadedAny = posts.get('length') > 0;
    this.set('canLoadMore', loadedAny);

    this.set('_minId', posts.get('lastObject.id'));
    this.set('_minUpdatedAt', posts.get('lastObject.updated_at').toISOString());
  }
});

export default class PostsRoute extends Route {
  @service infinity

  model() {
    return this.infinity.model('post', {}, ExtendedInfinityModel);
  }
}

Static parameters

You can also provide additional static parameters to infinityModel that will be passed to your backend server in addition to the pagination params. For instance, in the following example a category parameter is added:

return this.infinity.model('product', { perPage: 12, startingPage: 1,
                                       category: 'furniture' });

Extending InfinityModel

As of 1.0+, you can override or extend the behavior of Ember Infinity by providing a class that extends InfinityModel as a third argument to the Route#infinityModel hook.

import InfinityModel from '@eflexsystems/ember-infinity/lib/infinity-model';

const ExtendedInfinityModel = InfinityModel.extend({
  buildParams() {
    let params = this._super(...arguments);
    params['category_id'] = get(this, 'global.categoryId');
    return params;
  }
});

export default class ProductsRoute extends Route {
  @service infinity
  @service global

  @computed('global.categoryId')
  get categoryId() {
    return get(this, 'global.categoryId');
  }

  model() {
    const { global } = this;
    this.infinity.model('product', {}, ExtendedInfinityModel.extend({ global }));
  }
}

There is a lot you can do with this! Here is a simple use case where, say you have an API that does not return total_pages or count and you also don't need a loading spinner. Just set canLoadMore to true and @eflexsystems/ember-infinity will always try to fetch new records when the infinity-loader comes into viewport.

import InfinityModel from '@eflexsystems/ember-infinity/lib/infinity-model';

class ExtendedInfinityModel extends InfinityModel {
  canLoadMore = true;
}

export default class ProductsRoute extends Route {
  @service infinity

  model() {
    this.infinity.model('product', {}, ExtendedInfinityModel.extend());
  }
}

Model Public Properties

• isLoaded

isLoaded says if the model is loaded after fetching results

• loadingMore

loadingMore says if the model is currently loading more items

• isError

isError says if the fetch failed

Model Event Hooks

The infinity model also provides following hooks:

afterInfinityModel

In some cases, a single call to your data store isn't enough. The afterInfinityModel method is available for those cases when you need to chain together functions or promises after fetching a model.

As a simple example, let's say you had a blog and just needed to set a property on each Post model after fetching all of them:

Using the @eflexsystems/ember-infinity Service approach

import Route from '@ember/routing/route';
import InfinityModel from '@eflexsystems/ember-infinity/lib/infinity-model';

const ExtendedInfinityModel = InfinityModel.extend({
  afterInfinityModel(posts) {
    this.setEach('author', 'Jane Smith');
  }
});

export default class PostsRoute extends Route {
  @service infinity

  model() {
    return this.infinity.model('post', {}, ExtendedInfinityModel);
  }
}

As a more complex example, let's say you had a blog with Posts and Authors as separate related models and you needed to extract an association from Posts. In that case, return the collection you want from afterInfinityModel:

import Route from '@ember/routing/route';
import InfinityModel from '@eflexsystems/ember-infinity/lib/infinity-model';

const ExtendedInfinityModel = InfinityModel.extend({
  afterInfinityModel(posts) {
    return posts.mapBy('author').uniq();
  }
});

export default class PostsRoute extends Route {
  @service infinity

  model() {
    return this.infinity.model('post', {}, ExtendedInfinityModel);
  }
}

afterInfinityModel should return either a promise, ArrayProxy, or a falsy value. The returned value, when not falsy, will take the place of the resolved promise object and, if it is a promise, will hold execution until resolved. In the case of a falsy value, the original promise result is used.

So relating this to the examples above... In the first example, afterInfinityModel does not have an explicit return defined so the original posts promise result is used. In the second example, the returned collection of authors is used.

infinityModelUpdated

Triggered on the route whenever new objects are pushed into the infinityModel.

Args:

• lastPageLoaded

• totalPages

• infinityModel

infinityModelLoaded

Triggered on InfinityModel when is fully loaded.

Args:

• totalPages

import Route from '@ember/routing/route';
import InfinityModel from '@eflexsystems/ember-infinity/lib/infinity-model';

const ExtendedInfinityModel = InfinityModel.extend({
  infinityModelUpdated({ lastPageLoaded, totalPages, newObjects }) {
    Ember.Logger.debug('updated with more items');
  },
  infinityModelLoaded({ totalPages }) {
    Ember.Logger.info('no more items to load');
  }
});

export default class ProductsRoute extends Route {
  @service infinity

  model() {
    return this.infinity.model('product', { perPage: 12, startingPage: 1 }, ExtendedInfinityModel);
  }
}

Custom store

Chances are you'll want to scroll some source other than the default ember-data store to infinity. You can do that by injecting your store into the route and specifying the store to the infinityModel options:

import { inject as service } from '@ember/service';

export default class ProductsRoute extends Route {
  @service infinity
  @service('my-custom-store') customStore

  model(params) {
    return this.infinity.model('product', {
      perPage: 12,
      startingPage: 1,
      store: this.customStore, // custom ember-data store or ember-redux / ember-cli-simple-store / your own hand rolled store (see dummy app)
      storeFindMethod: 'findAll' // should return a promise (optional if custom store method uses `query`)
    })
  }
}

Infinity Loader

The infinity-loader component as some extra options to make working with it easy! It is based on the IntersectionObserver API. In essence, instead of basing your scrolling on Events (synchronous), it instead behaves asynchronously, thus not blocking the main thread.

https://developer.mozilla.org/en-US/docs/Web/API/Intersection_Observer_API

• infinityLoad

Closure actions are enabled in the 1.0.0 series.

<InfinityLoader
  @infinityModel={{model}}
  @infinityLoad={{action "loadMoreProducts"}} />

• hideOnInfinity

<InfinityLoader
  @infinityModel={{model}}
  @hideOnInfinity={{true}} />

Now, when the Infinity Model is fully loaded, the infinity-loader will hide itself and set isDoneLoading to true.

Versions less than 1.0.0 called this property destroyOnInfinity

• developmentMode

<InfinityLoader
  @infinityModel={{model}}
  @infinityLoad={{action "loadMoreProducts"}}
  @developmentMode={{true}} />

This simply stops the infinity-loader from fetching triggering loads, so that you can work on its appearance.

• loadingText & loadedText

<InfinityLoader
  @infinityModel={{model}}
  @infinityLoad={{action "loadMoreProducts"}}
  loadingText="Loading..."
  loadedText="Loaded!" />

By default, the infinity-loader will just output a span showing its status.

• Providing a block

{{#infinity-loader infinityModel=model infinityLoad=(action "infinityLoad")}}
  <img src="loading-spinner.gif" />
{{/infinity-loader}}

If you provide a block to the component, it will render the block instead of rendering loadingText or loadedText. This will allow you to provide your own custom markup or styling for the loading state.

• reached-infinity Class Name

.infinity-loader {
  background-color: wheat;
  &.reached-infinity {
    background-color: lavender;
  }
}

When the Infinity Model loads entirely, the reached-infinity class is added to the component.

• infinity-template generator

ember generate infinity-template

Will install the default infinity-loader template into your host app, at app/templates/components/infinity-loader.

• scrollable

<InfinityLoader @scrollable="#content" />

You can optionally pass in a CSS style selector string. If not present, scrollable will default to using the window. This is useful for scrollable areas that are constrained in the window.

• loadPrevious

<InfinityLoader @loadPrevious={{true}} />

<ul>...</ul>

<InfinityLoader />

To load elements above your list on load, place an infinity-loader component above the list with `loadPrevious=true`.

• triggerOffset

<InfinityLoader @triggerOffset={{offset}} />

You can optionally pass an offset value. This value will be used when calculating if the bottom of the scrollable has been reached.

• eventDebounce

<InfinityLoader @eventDebounce={{50}} />

Default is 50ms. You can optionally pass a debounce time to delay loading the list when reach bottom of list

Use @eflexsystems/ember-infinity with button

You can use the service loading magic of @eflexsystems/ember-infinity without using the InfinityLoader component.

load-more-button.js:

export default class InfinityComponent extends Component {
  @service infinity

  loadText = 'Load more';
  loadedText = 'Loaded';

  onClick() {
    this.infinity.infinityLoad(this.infinityModel);
  }
}

load-more-button.hbs:

{{#if @infinityModel.reachedInfinity}}
  <button>{{loadedText}}</button>
{{else}}
  <button>{{loadText}}</button>
{{/if}}

template.hbs:

<ul class="test-list">
{{#each @model as |item|}}
  <li>{{item.name}}</li>
{{/each}}
</ul>

<LoadMoreButton @infinityModel={{model}} />

Delay start of infinite loading until user has indicated they would like to load more

template.hbs:

{{#if hasClickedLoadMore}}
  {{infinity-loader infinityModel=model triggerOffset=400}}
{{else}}
  <button {{action (toggle 'hasClickedLoadMore' this)}}>Load more</button>
{{/if}}

Load Previous Pages

The basic idea here is to:

1. Place an infinity-loader component above and below your content.
2. Ensure loadPrevious is set to true on the infinity-loader above the content.

If your route loads on page 3, it will fetch page 2 on load. As the user scrolls up, it will fetch page 1 and stop loading from there. If you are already on page 1, no actions will be fired to fetch the previous page.

<ul>
<InfinityLoader
  @infinityModel={{model}}
  @loadPrevious={{true}}
  @loadedText={{null}}
  @loadingText={{null}} />

{{#each @model as |item|}}
  <li>{{item.id}}. {{item.name}}</li>
{{/each}}

<InfinityLoader
  @infinityModel={{model}}
  @loadingText="Loading more awesome records..."
  @loadedText="Loaded all the records!"
  @triggerOffset={{500}} />
</ul>

Ember Concurrency Usage

Coming

Testing

Testing can be a breeze once you have an example. So here is an example! Note this is using Ember's new testing APIs.

import { find, findAll, visit, waitFor, waitUntil } from '@ember/test-helpers';

test('fetches more data when scrolled into viewport', async function(assert) {
  await visit('/infinity-scrollable');

  assert.equal(findAll('.t-items').length, 10);
  assert.equal(findAll('.infinity-scrollable.inactive').length, 1, 'component is inactive before fetching more data');
  document.querySelector('.infinity-scrollable').scrollIntoView();

  await waitFor('.infinity-scrollable.inactive');

  assert.equal(findAll('.t-items').length, 20);
  assert.equal(findAll('.infinity-scrollable.inactive').length, 1, 'component is inactive after fetching more data');
});

test('fetch more data using waitUntil', async function(assert) {
  await visit('/infinity-scrollable');

  assert.equal(findAll('.t-items').length, 10);
  assert.equal(findAll('.infinity-scrollable.inactive').length, 1, 'component is inactive before fetching more data');
  document.querySelector('.infinity-scrollable').scrollIntoView();

  await waitUntil(() => {
    return findAll('.t-items').length === 20;
  });

  assert.equal(findAll('.t-items').length, 20);
  assert.equal(findAll('.infinity-scrollable.inactive').length, 1, 'component is inactive after fetching more data');
});