lom_atom

lom_atom

State management with error handling and reactive cache done right.

Alternative standalone implementation of eigenmethod mol_atom.

• About 11kb minified
• Memory-efficient
• Simpler, less core concept than mobx
• Loading status / error handling features

Usage examples with reactive-di: example source, demo, todomvc benchmark

Install npm install --save lom_atom

• Observable property
• Observable get/set
• Controlling cache
• Method-style properties
• Computed values
• Side effects
• Key-value
• Actions

Observable property

import {mem} from 'lom_atom'
class Todo {
    @mem title = ''
}
const todo = new Todo()
todo.title = '123'

Observable get/set

import {mem} from 'lom_atom'
class Todo {
    @mem set title(next: string) {
        // test next
    }
    @mem get title(): string {
        return 'default'
    }
}
const todo = new Todo()
todo.title = '123'

Computed values

One decorator for all cases.

class TodoList {
    @mem todos = []
    @mem get unfinishedTodos() {
        return this.todos.filter((todo) => !todo.finished)
    }
}

Like mobx, unfinishedTodos is updated automatically when a todo changed.

Side effects

Lom atom memoized property can interact with upstream (server, etc). Each observable or computed property can be used in 4 cases: get, set, cache set, cache reset. Modifiers helps to produce and control side effects for making network requests.

import {mem} from 'lom_atom'

class TodoList {
    @mem set todos(todos: Todo | Error) {
        fetch({
            url: '/todos',
            method: 'POST',
            body: JSON.stringify(todos)
        })
            .then((data) => mem.cache(this.todos = data))
            .catch(error => mem.cache(this.todos = error))

        console.log('set handler')

        throw new mem.Wait()
    }

    @mem get todos(): Todos {
        console.log('get handler')

        fetch('/todos')
            .then((data) => mem.cache(this.todos = data))
            .catch(error => mem.cache(this.todos = error))

        throw new mem.Wait()
    }

    @mem.manual get user(): IUser {
        fetch('/user')
            .then((data) => mem.cache(this.user = data))
            .catch(error => mem.cache(this.user = error))
    }

    set user(next: IUser | Error) {}

    @mem todosWithUser() {
        return {todos: this.todos, user: this.user}
    }

    @mem todosWithUserParallel() {
        return {todos: mem.async(this.todos), user: mem.async(this.user)}
    }
}
const list = new TodoList()

• this.todos - get value, if cache is empty - invokes get todos and actualize cache.
• this.todos = data - set value, if cache empty - pass value to set todos() {} and actualize cache.
• mem.cache(this.todos = data) - set new value or error directly into cache (push).
• mem.cache(list.todosWithUser) - deep reset cache for todosWithUser all its dependencies (todos) and notify all dependants about changes.
• @mem.manual get user() {...} - exclude user from deep reset. mem.reset(list.todosWithUser) resets todos but not user. If you want to reset user, use helper directly on user: mem.cache(list.user)
• mem.async(this.todos) - initiate parallel loading todos and user (wrap error in proxy, do not throw error if data are fetching).

Key-value

Basic dictionary support. First argument is an key of any type. See eigenmethod mol_mem.

class TodoList {
    @mem.key todo(id: string, next?: Todo): Todo {
        if (next === undefined) {
            // get mode
            return {}
        }

        return next
    }
}
const list = new TodoList()
list.todo('1', {id: 1, title: 'Todo 1'}) // set todo
list.todo('1') // get todo

Actions

State updates are asynchronous, but sometime we need to do transactional synced updates via action helper:

import {action, mem} from 'lom_atom'
class Some {
    @mem name = ''
    @mem id = ''

    @action set(id: string, name: string) {
        this.id = id
        this.name = name
    }
}
const some = new Some()

// Transactionally changed in current tick:
action(() => {
    some.name = 'test'
    some.id = '123'
})

// or

some.set('123', 'test')

Changelog

3.1.2 (2017-12-25)

<a name="3.1.1"></a>