redux-combiner
v0.4.4
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Convenient reducers combiner for Redux
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redux-combiner
redux-combiner proposes a way to describe possible application state changes as a tree of reducers reacting on specific actions.
Description
A reducers tree consists of nodes, and its structure corresponds to an application state. A node describes its subtree and registers actions reducers on the node. A node must be initialized with its subtree or specific default value, this way reducers tree defines default application state. Each node of the tree returns just a normal reducer, and each such node is able to contain other nodes or plain old switch-case reducers within its subtree. All these forces decomposition, and makes reducers more focused on related state changes. This also means that you able to integrate redux-combiner gradually into your projects by substituting or wrapping your existing reducers with redux-combiner nodes.
Example
To get a better sense let's modify Redux to-do list reducers example with redux-combiner:
import { createStore } from 'redux'
import { node, demux } from 'redux-combiner'
const reducer = node({
todos: demux(
[],
{
completed: node(false)
.on('TOGGLE_TODO', completed => !completed)
},
(todos, action) => todos.findIndex(todo => todo.id === action.id)
)
.on('ADD_TODO', (todos, action) => [
...todos,
{
id: action.id,
text: action.text,
completed: false
}
]),
visibilityFilter: node('SHOW_ALL')
.on('SET_VISIBILITY_FILTER', (filter, action) => action.filter)
})
store = createStore(reducer)
redux-combiner comes with two kinds of nodes: node
and demux
. node
is just a normal node: it describes its subtree and registers reducers on the node. demux
(demultiplexer) is a bit special one: it also expects that described node is a collection of nodes with a specific structure, and each such node can be uniquely addressed within the collection. So, from the example, we can see that todos
array is described by demux
node, and each item can have its property completed
to be toggled on TOGGLE_TODO
action. Which item to pick is determined by the action id
property.
From the example we can also see that there is no need for switch-case reducers and that propagation of state changes is handled for you, though you still need to return new values from your reducers when actual changes happen (as in ADD_TODO
reducer in the example).
To be efficent, redux-combiner uses information on expected actions of each reducers subtree and calls only related subtrees. So, in the example, only visibilityFilter
subtree will be called on SET_VISIBILITY_FILTER
action.
And that's basically it! As you can see, redux-combiner has really simple yet powerful API which can be further customized. See docs for more!
Performance
redux-combiner has quite decent performance, as js-framework-benchmark shows. It's quite close to bare React version of the benchmark.
Installation
npm i --save redux-combiner
Documentation
combiner ( combineReducers ) -> { node, demux }
default
export of redux-combiner is combiner
function that creates customized nodes. combiner
's
only argument is combineReducers
to use to combine reducers tree.
This is useful to support custom combineReducers
, for example, redux-loop
's one.
Please note, that only combineReducers
working with plain js object are supported at the moment. For more details see limitations.
node ( initial ) -> Function (state, action)
node
is a node initialized with default combineReducers
.
initial
describes initial state or subtree of reducers tree with some other nodes within it. Children nodes may be placed arbitrary deep within the subtree. The subtree may have primitive leafs.
demux ( initial, [ itemSchema ], [ selector ] ) -> Function (state, action)
demux
is a demux node initialized with default combineReducers
.
initial
is similar to node
's, but it's expected to be a collection of similar elements. The collection is not necessary an array, objects also may be used as collections of values.
itemSchema
describes each collection item subtree.
selector
is used to select item or items of the collection to apply specific action. selector
may be either a function or a property name to get on an action. If selector
is a function it must return either action property name, or iterator of such property names. If selector
is omitted, it defaults to 'index'
for array states or to 'id'
for object states.
selector
function signature is reducer-like: (state, action)
, where state
corresponds to state subtree of the node.
selector
should not depend on action
type, because it's just a mean of addressing. If your selector
depends on action
type that means your addressing is inconsistent. But there may be cases when you need to select items in different ways. The suggested approach is to wrap a demux as a child of another one.
node#on ( actions, reducers ) -> node
Registers reducers on specific actions on the node. Returns the same node to allow chaining.
reducers
is either a function or array of functions. If reducers
is an array, than all reducers will be called on the action in order (similar to reduce-reducers
).
actions
is either action type or an array of action types. If actions
is an array, than all corresponding reducers are called on each action in order.
combineReducers -> Function ( state, action )
redux-combiner version of combineReducers is quite similar to Redux' one. The main difference is that it supports arrays as roots of composition:
import { combineReducers } from 'redux-combiner'
import reducers from './reducers'
combineReducers([ ...reducers ])
Limitations
Currently only plain js object states are supported, because of notion overlapping between reducers tree structure and state representation. But it should be quite easy to add support for less trivial structures, such as Immutable.js structures, by splitting these concepts.