Customizing the Aurelia dependency injection behaviors

myModel.js

// MyModel is a class that represents a database object.
export class MyModel {
  name;
  address;
  telephone;
  
  constructor(obj) {
    this.name = obj.name;
    this.address = obj.address;
    this.telephone = obj.telephone;
  }
}

myViewModel.js

import { Factory, inject } from 'aurelia-framework'; // or 'aurelia-dependency-injection';
import { MyModel } from './myModel';
import { State } from './state';

// Factory.of tells the Aurelia DI container that you're not looking for an instantiated object, but a constructor such that you can 
// manually instantiate objects. This is particularly useful when you need to create multiple instances of an object or when you 
// need to manually pass arguments to the constructor or both.

@inject(Factory.of(MyModel), State)
export class MyViewModel {
 
  models = [];
  
  constructor(myModelFactory, state) {
    this.createMyModel(obj) => { 
      const myModel = myModelFactory(obj);
      models.push(myModel);
      return myModel;
    }
    
    this.state = state;
    state.mode = 'edit';
    state.currentMyModel = {
      name: '',
      address: '',
      telephone: ''
    };
    state.update();
  }
}

state.js

import { transient } from 'aurelia-framework'; // or 'aurelia-dependency-injection';

// State is an object that tracks the state of an object. You can set arbitrary values on the State object and track changes. 
// Every time we inject the State class we want a new object instantiated, to prevent the state of one object from interfering 
// with the state of another object. Therefore, we use the `transient` decorator to tell Aurelia to create a new instance every 
// time it is injected.

@transient()
export class State {

  constructor() {
    let originalState;
    this.update = () => originalState = clone(this);
    this.revert = () => Object.assign(this, originalState);
    Object.defineProperty(this, 'isDirty', {
      get: () => JSON.stringify(this) !== JSON.stringify(originalState)
    });
    this.update();
  }
}

// deep copy
function clone(obj) {
  return JSON.parse(JSON.stringify(obj));
}