Cork App Utils

• Install
• BaseModel
• BaseService
• BaseStore
• EventBus
• Wiring to UI
• CLI

Install

npm i -s @ucd-lib/cork-app-utils 

Overview

BaseModel

The BaseModel exposes the event bus and has helper methods for registering with the global model registry. This global object is used by Element interface mixins to inject the models into elements.

Attributes

• eventBus : EventBus

Methods

• register(name: String)
  • Register the model
• emit(event: String, payload: Object)
  • Emit event to event bus

Example Usage

import {BaseModel} from '@ucd-lib/cork-app-utils';
import ExampleStore from '../stores/ExampleStore';
import ExampleService from '../service/ExampleService');

class ExampleModel extends BaseModel {

  constructor() {
    super();

    this.store = ExampleStore;
    this.service = ExampleService;

    this.register('ExampleModel');

    // If you want to add other models
    // this.inject('AnotherModel');
    // Make sure in your main index.js file to call
    // import {Registry} from '@ucd-lib/cork-app-utils';
    // // import models
    // Registry.ready();
  }

  /**
   * @method get
   * @description In this example we will fetch some data
   * using our service.  The service may return some
   * data already cached in the store.  The returned 
   * data will be in a State Payload Wrapper.
   *
   * @returns {Promise}
   */
  async get(id) {
    // get current state
    let state = this.store.get(id);

    // wait for the service to do it's thing
    // if you are interested in the loading events
    // you will want to set event listeners
    try {

      // check to see if we are already loading this resource
      if( state.state === 'loading' ) {
        // make sure you store the request promise in the store as 'request'
        // then you can await here on it as a semaphore, preventing duplicate 
        // requests if multiple UI elements request a resource at the same time
        await state.request;
      } else {
        // the return from the service is the network respons
        // not the state response which is stored in the store
        await this.service.get(id);
      }

    } catch(e) {
      // handle network error here if you want to handle in model
      // but error state should be capture by store and UI elements 
      // should react to the error state event
    }

    // regardless of the network success/failure of request above
    // return the current state
    return this.store.get(id);
  }

  /**
   * @method set
   * @description Update some app state
   */
  set(data) {
    this.store.update(data)
  }
}

const exampleModel = new ExampleModel();
export default exampleModel;

Loading Models

Here is a sample index.js file for the ./src folder. Where ./src contains ./src/models, ./src/services, ./src/stores, etc.

index.js:

import {Registry} from '@ucd-lib/cork-app-utils';

import ExampleModel from './models/ExampleModel.js';
import AnotherModel from './models/AnotherModel.js';

// This handles inject of other models into models, avoiding
// cyclical dependency issues
Registry.ready();

// then if you want to expose
// export {ExampleModel, AnotherModel};
// or
// if( typeof window !== 'undefined' ) {
//   window.APP_MODELS = {ExampleModel, AnotherModel};
// }

BaseService

The BaseService exposes helper functions to call rest services

Attributes

• eventBus : EventBus

Methods

• request(options: Object)
  • Make a fetch request

Example Usage

import {BaseService} from '@ucd-lib/cork-app-utils');
import ExampleStore from '../stores/ExampleStore');

class ExampleService extends BaseService {

  constructor() {
    super();

    this.store = ExampleStore;
  }

  async get(id) {
    return this.request({
      url : `/api/get/${id}`,
      // optional
      // if the state is 'loading' and another request for this object
      // comes in, both requests will wait on the same promise preventing
      // two network requests for the same object
      checkCached : () => this.store.data.byId[id],
      // request is a promise to resolves when network request finished (success or failure)
      onLoading : request => this.store.setLoading(id, request),
      onLoad : result => this.store.setLoaded(id, result.body),
      onError : e => this.store.setError(id, e)
    });
  }
}

const exampleService = new ExampleService();
export default exampleService;

BaseStore

The ServiceModel exposes helper functions to call rest services

Attributes

• eventBus : EventBus

Methods

• request(options: Object)
  • Make a fetch request

Example Usage

import {BaseStore} from '@ucd-lib/cork-app-utils';

class ExampleStore extends BaseStore {

  constructor() {
    super();

    this.data = {
      byId : {}
    }

    this.events = {
      EXAMPLE_UPDATE = 'example-update'
    }
  }

  // request is the network request promise
  // always store this so we can wait on it if a second
  // entity requests this same resource
  setLoading(id, request) {
    this._setState({
      state: this.STATE.LOADING, 
      id, request
    });
  }

  setLoaded(id, payload) {
    this._setState({
      state: this.STATE.LOADED,   
      id, payload
    });
  }

  setError(id, error) {
    this._setState({
      state: this.STATE.ERROR,   
      id, error
    });
  }

  _setState(id, state) {
    // optionally check that state has actually changed
    // this is helpful to prevent multiple events of same state that sometimes occur
    // if( !this.stateChanged(this.data.byId[id], state) ) return;

    this.data.byId[id] = state
    this.emit(this.events.EXAMPLE_UPDATE, state);
  }
}

const exampleStore = ExampleStore();
export default exampleStore;

EventBus

Global instance of EventEmitter class.

Wiring to UI

LitElement

import { LitElement } from 'lit-element';
import render from "./my-element.tpl.js"

// sets globals Mixin and EventInterface
import "@ucd-lib/cork-app-utils";

export default class MyElement extends Mixin(LitElement)
  .with(LitCorkUtils) {

  constructor() {
    super();
    this.render = render.bind(this);

    this._injectModel('ExampleModel');
  }

  showData(id) {
    let data = await this.ExampleModel.get('someId');
    // you can do stuff with
  }

  // LitCorkUtils will automatically wire up this method
  // to the example-update event.
  _onExampleUpdate(e) {
    if( e.state === 'loading' ) {

    } else if( e.state === 'loaded' ) {

    } else if( e.state === 'error' ) {

    }
  }

  _setExample() {
    this.ExampleModel.set({
      my : 'new state'
    });
  }
}

customElements.define('my-element', MyElement);

CLI

Install cork-app-utils globally

npm i -g @ucd-lib/cork-app-utils 

The command line utility has two main helpers:

Model Template

In the src or lib directory or your client code, run:

cork-app-utils model example

It will create the following files (and folders if they do not exist):

• lib/models/ExampleModel.js
• lib/services/ExampleService.js
• lib/stores/ExampleStore.js

With boiler plate wiring code already in place.

Lit Element Template

In the directory you wish to create a new element run:

cork-app-utils lit my-element

This will create the following files:

• my-element.js
• my-element.tpl.js

Where the .js file contains the main element definition and .tpl.js contains the template tag. There is nothing specific to cork-app-utils in the Lit template other than the way we like to split the elements into two files. To bind a Lit Element to a stores events, see the Lit Element section in Wiring to UI.