react-observable-mutations (ROM)

The ROM – an observable pattern based library. It can be used as an app state managment, that focuses on the mutations of the observable objects: DomainEntities, ViewModels, Services, etc. The lib doesn't allow to subscribe to changes of object's properties, lists or primitive values. In addition, subscriptions are registered manually, that makes the ROM more transparent and flexible than MobX.

As an example, let's create a simple ToDo App

Our domain model has only a ToDo-Task:

export class Task extends Observable {
  private readonly _text: string
  get text(): string {
    return this._text
  }

  private _isDone: boolean
  get isDone(): boolean {
    return this._isDone
  }

  constructor(text: string) {
    super('TodoTask')
    this._text = text
    this._isDone = false
  }

  done() {
    this._isDone = true
    this.mutated()
  }
}

The ViewModel contains a list of tasks:

export class TodoListVM extends Observable {
  tasks: Task[]

  constructor() {
    super('TodoListVM')
    this.tasks = []
  }

  addTask(text: string) {
    this.tasks.push(new Task(text))
    this.mutated()
  }
}

The TodoListView must be rendered only after a new task is added. The TaskView must be rendered after a new task is added or the task's status is changed. For this we have to use observer and observe function-wrappers:

const todoListVM = new TodoListVM()

export const TodoListView = observer(() => {
  const vm = observe(todoListVM)
  return <div>
    <p>     Todo App     </p>
    <p>------------------</p>
    {vm.tasks.map(task => {
      return <TaskView key={task.text}
                       task={task}/>
    })}
    <p>------------------</p>
    <button onClick={() => { vm.addTask('Task ' + (vm.tasks.length + 1)) }}>
    Add Task
    </button>
  </div>
})

interface TaskViewProps {
  task: Task
}
export const TaskView = observer((props: TaskViewProps) => {
  const task = observe(props.task)
  return (
    <p onClick={() => { task.done() }}>
      {task.text + (task.isDone ? ': DONE' : ': IN PROGRESS')}
    </p>
  )
})

You can subscribe to any observed object directly:

const t = new Task(text)
const handler = () => { console.log('Task has mutated!') }
const unsubscribe = t.subscribe(handler)
// unsubscribe()

Install

npm i react-observable-mutations

License

MIT