@austinlangdon/redux-orm

Redux-ORM

Installation

npm install redux-orm --save

Or with a script tag exposing a global called ReduxOrm:

<script src="https://unpkg.com/redux-orm/dist/redux-orm.min.js"></script>

• Latest browser build (minimized)

  • Source Map

• Latest browser build (only use if size does not matter)

Polyfill

Redux-ORM uses some ES2015+ features, such as Set. If you are using Redux-ORM in a pre-ES2015+ environment, you should load a polyfill like babel-polyfill before using Redux-ORM.

Extensions

• redux-orm-proptypes: React PropTypes validation and defaultProps mixin for Redux-ORM Models

Usage

For a detailed walkthrough see a guide to creating a simple app with Redux-ORM. Its not up-to-date yet but the code has a branch for version 0.9. The Redux docs have a short section on Redux-ORM as well.

Declare Your Models

You can declare your models with the ES6 class syntax, extending from Model. You need to declare all your non-relational fields on the Model, and declaring all data fields is recommended as the library doesn't have to redefine getters and setters when instantiating Models. Redux-ORM supports one-to-one and many-to-many relations in addition to foreign keys (oneToOne, many and fk imports respectively). Non-related properties can be accessed like in normal JavaScript objects.

// models.js
import { Model, fk, many, attr } from 'redux-orm';

class Book extends Model {
    toString() {
        return `Book: ${this.name}`;
    }
    // Declare any static or instance methods you need.
}
Book.modelName = 'Book';

// Declare your related fields.
Book.fields = {
    id: attr(), // non-relational field for any value; optional but highly recommended
    name: attr(),
    // foreign key field
    publisherId: fk({
        to: 'Publisher',
        as: 'publisher',
        relatedName: 'books',
    }),
    authors: many('Author', 'books'),
};

export default Book;

Register Models and Generate an Empty Database State

Defining fields on a Model specifies the table structure in the database for that Model. In order to generate a description of the whole database's structure, we need a central place to register all Models we want to use.

An instance of the ORM class registers Models and handles generating a full schema from all the models and passing that information to the database. Often you'll want to have a file where you can import a single ORM instance across the app, like this:

// orm.js
import { ORM } from 'redux-orm';
import { Book, Author, Publisher } from './models';

const orm = new ORM({
  stateSelector: state => state.orm,
});
orm.register(Book, Author, Publisher);

export default orm;

You could also define and register the models to an ORM instance in the same file, and export them all.

Now that we've registered Models, we can generate an empty database state. Currently that's a plain, nested JavaScript object that is structured similarly to relational databases.

// index.js

import orm from './orm';

const emptyDBState = orm.getEmptyState();

Applying Updates to the Database

When we have a database state, we can start an ORM session on that to apply updates. The ORM instance provides a session method that accepts a database state as it's sole argument, and returns a Session instance.

const session = orm.session(emptyDBState);

Session-specific classes of registered Models are available as properties of the session object.

const Book = session.Book;

Models provide an interface to query and update the database state.

Book.withId(1).update({ name: 'Clean Code' });
Book.all().filter(book => book.name === 'Clean Code').delete();
Book.idExists(1)
// false

The initial database state is not mutated. A new database state with the updates applied can be found on the state property of the Session instance.

const updatedDBState = session.state;

Redux Integration

To integrate Redux-ORM with Redux at the most basic level, you can define a reducer that instantiates a session from the database state held in the Redux state slice, then when you've applied all of your updates, you can return the next state from the session.

import orm from './orm';

function ormReducer(dbState, action) {
    const sess = orm.session(dbState);

    // Session-specific Models are available
    // as properties on the Session instance.
    const { Book } = sess;

    switch (action.type) {
    case 'CREATE_BOOK':
        Book.create(action.payload);
        break;
    case 'UPDATE_BOOK':
        Book.withId(action.payload.id).update(action.payload);
        break;
    case 'REMOVE_BOOK':
        Book.withId(action.payload.id).delete();
        break;
    case 'ADD_AUTHOR_TO_BOOK':
        Book.withId(action.payload.bookId).authors.add(action.payload.author);
        break;
    case 'REMOVE_AUTHOR_FROM_BOOK':
        Book.withId(action.payload.bookId).authors.remove(action.payload.authorId);
        break;
    case 'ASSIGN_PUBLISHER':
        Book.withId(action.payload.bookId).publisherId = action.payload.publisherId;
        break;
    }

    // the state property of Session always points to the current database.
    // Updates don't mutate the original state, so this reference is not
    // equal to `dbState` that was an argument to this reducer.
    return sess.state;
}

Previously we advocated for reducers specific to Models by attaching a static reducer function on the Model class. If you want to define your update logic on the Model classes, you can specify a reducer static method on your model which accepts the action as the first argument, the session-specific Model as the second, and the whole session as the third.

class Book extends Model {
    static reducer(action, Book, session) {
        switch (action.type) {
        case 'CREATE_BOOK':
            Book.create(action.payload);
            break;
        case 'UPDATE_BOOK':
            Book.withId(action.payload.id).update(action.payload);
            break;
        case 'REMOVE_BOOK':
            const book = Book.withId(action.payload);
            book.delete();
            break;
        case 'ADD_AUTHOR_TO_BOOK':
            Book.withId(action.payload.bookId).authors.add(action.payload.author);
            break;
        case 'REMOVE_AUTHOR_FROM_BOOK':
            Book.withId(action.payload.bookId).authors.remove(action.payload.authorId);
            break;
        case 'ASSIGN_PUBLISHER':
            Book.withId(action.payload.bookId).publisherId = action.payload.publisherId;
            break;
        }
        // Return value is ignored.
        return undefined;
    }

    toString() {
        return `Book: ${this.name}`;
    }
}

To get a reducer for Redux that calls these reducer methods:

import { createReducer } from 'redux-orm';
import orm from './orm';

const reducer = createReducer(orm);

This reducer needs to be hooked into your Redux store. Make sure that the key under which you store it is also the key that you use to retrieve the ORM's state in its stateSelector. Otherwise selectors won't work properly.

createReducer is really simple, so we'll just paste the source here.

function createReducer(orm, updater = defaultUpdater) {
    return (state, action) => {
        const session = orm.session(state || orm.getEmptyState());
        updater(session, action);
        return session.state;
    };
}

function defaultUpdater(session, action) {
    session.sessionBoundModels.forEach(modelClass => {
        if (typeof modelClass.reducer === 'function') {
            modelClass.reducer(action, modelClass, session);
        }
    });
}

As you can see, it just instantiates a new Session, loops through all the Models in the session, and calls the reducer method if it exists. Then it returns the new database state that has all the updates applied.

Use with React

Use memoized selectors to make queries into the state. Redux-ORM uses smart memoization: the below selector accesses Author and AuthorBooks branches (AuthorBooks is a many-to-many branch generated from the model field declarations), and the selector will be recomputed only if those branches change. The accessed branches are resolved on the first run.

// selectors.js
import { createSelector } from 'redux-orm';
import orm from './orm';

const authorSelector = createSelector(
    orm,
    session => {
        return session.Author.all().toModelArray().map(author => {
            /**
             * author is a model instance and exposes relationship accessors
             * such as author.books …
             *
             * This gets a reference to the model's underlying object
             * which has no such accessors, containing only raw attributes.
             */
            const { ref } = author;
            // Object.keys(ref) === ['id', 'name']

            return {
                ...ref,
                books: author.books.toRefArray().map(book => book.name),
            };
        });
    }
);

// Will result in something like this when run:
// [
//   {
//     id: 0,
//     name: 'Tommi Kaikkonen',
//     books: ['Introduction to Redux-ORM', 'Developing Redux applications'],
//   },
//   {
//     id: 1,
//     name: 'John Doe',
//     books: ['John Doe: an Autobiography']
//   }
// ]

Selectors created with createSelector can be used as input to any additional reselect selectors you want to use. They are also great to use with redux-thunk: get the whole state with getState(), pass the ORM branch to the selector, and get your results. A good use case is serializing data to a custom format for a 3rd party API call.

Because selectors are memoized, you can use pure rendering in React for performance gains.

// components.js
import React from 'react';
import { authorSelector } from './selectors';
import { connect } from 'react-redux';

function AuthorList({ authors }) {
    const items = authors.map(author => (
        <li key={author.id}>
            {author.name} has written {author.books.join(', ')}
        </li>
    ));

    return (
        <ul>{items}</ul>
    );
}

function mapStateToProps(state) {
    return {
        authors: authorSelector(state),
    };
}

export default connect(mapStateToProps)(AuthorList);

Understanding Redux-ORM

An ORM?

Well, yeah. Redux-ORM deals with related data, structured similar to a relational database. The database in this case is a simple JavaScript object database.

Why?

For simple apps, writing reducers by hand is alright, but when the number of object types you have increases and you need to maintain relations between them, things get hairy. ImmutableJS goes a long way to reduce complexity in your reducers, but Redux-ORM is specialized for relational data.

Immutability

Say we start a session from an initial database state situated in the Redux atom, update the name of a certain book.

First, a new session:

import { orm } from './models';

const dbState = store.getState().orm; // getState() returns the Redux state
const sess = orm.session(dbState);

The session maintains a reference to a database state. We haven't updated the database state, therefore it is still equal to the original state.

sess.state === dbState
// true

Let's apply an update.

const book = sess.Book.withId(1)

book.name // 'Refactoring'
book.name = 'Clean Code'
book.name // 'Clean Code'

sess.state === dbState
// false

The update was applied, and because the session does not mutate the original state, it created a new one and swapped sess.state to point to the new one.

Let's update the database state again through the ORM.

// Save this reference so we can compare.
const updatedState = sess.state;

book.name = 'Patterns of Enterprise Application Architecture';

sess.state === updatedState
// true. If possible, future updates are applied with mutations. If you want
// to avoid making mutations to a session state, take the session state
// and start a new session with that state.

If possible, future updates are applied with mutations. In this case, the database was already mutated, so the pointer doesn't need to change. If you want to avoid making mutations to a session state, take the session state and start a new session with that state.

Customizability

Just like you can extend Model, you can do the same for QuerySet (customize methods on Model instance collections). You can also specify the whole database implementation yourself (documentation pending).

Caveats

The ORM abstraction will never be as performant compared to writing reducers by hand, and adds to the build size of your project. If you have very simple data without relations, Redux-ORM may be overkill. The development convenience benefit is considerable though.

API

ORM

See the full documentation for ORM here

Instantiation:

const orm = new ORM({
  stateSelector: state => state.orm, // wherever the reducer is put during createStore
});

Instance methods:

• register(...models: Array<Model>): registers Model classes to the ORM instance.
• session(state: any): begins a new Session with state.

Redux Integration

• createReducer(orm: ORM): returns a reducer function that can be plugged into Redux. The reducer will return the next state of the database given the provided action. You need to register your models before calling this.
• createSelector(orm: ORM, [...inputSelectors], selectorFunc): returns a memoized selector function for selectorFunc. selectorFunc receives session as the first argument, followed by any inputs from inputSelectors. Note that the first inputSelector must return the db-state to create a session from. Read the full documentation for details.

Model

See the full documentation for Model here.

Instantiation: Don't instantiate directly; use the class methods create and upsert as documented below.

Class Methods:

• withId(id): gets the Model instance with id id.
• idExists(id): returns a boolean indicating if an entity with id id exists in the state.
• exists(matchObj): returns a boolean indicating if an entity whose properties match matchObj exists in the state.
• get(matchObj): gets a Model instance based on matching properties in matchObj (if you are sure there is only one matching instance).
• create(props): creates a new Model instance with props. If you don't supply an id, the new id will be Math.max(...allOtherIds) + 1.
• upsert(props): either creates a new Model instance with props or, in case an instance with the same id already exists, updates that one - in other words it's create or update behaviour.

You will also have access to almost all QuerySet instance methods from the class object for convenience, including where and the like.

Instance Attributes:

• ref: returns a direct reference to the plain JavaScript object representing the Model instance in the store.

Instance methods:

• equals(otherModel): returns a boolean indicating equality with otherModel. Equality is determined by shallow comparison of both model's attributes.
• set(propertyName, value): updates propertyName to value. Returns undefined. Is equivalent to normal assignment.
• update(mergeObj): merges mergeObj with the Model instance properties. Returns undefined.
• delete(): deletes the record for this Model instance in the database. Returns undefined.

Subclassing:

Use the ES6 syntax to subclass from Model. Any instance methods you declare will be available on Model instances. Any static methods you declare will be available on the Model class in Sessions.

For the related fields declarations, either set the fields property on the class or declare a static getter that returns the field declarations like this:

Declaring fields:

class Book extends Model {
    static get fields() {
        return {
            id: attr(),
            name: attr(),
            author: fk('Author'),
        };
    }
}
// alternative:
Book.fields = {
    id: attr(),
    name: attr(),
    author: fk('Author'),
}

All the fields fk, oneToOne and many accept a single argument, the related model name. The fields will be available as properties on each Model instance. You can set related fields with the id value of the related instance, or the related instance itself.

For fk, you can access the reverse relation through author.bookSet, where the related name is ${modelName}Set. Same goes for many. For oneToOne, the reverse relation can be accessed by just the model name the field was declared on: author.book.

For many field declarations, accessing the field on a Model instance will return a QuerySet with two additional methods: add and remove. They take 1 or more arguments, where the arguments are either Model instances or their id's. Calling these methods records updates that will be reflected in the next state.

Relations support more configuration options like accessors, related names, etc. by passing an object:

class Book extends Model {
    static get fields() {
        return {
            id: attr(),
            name: attr(),
            authorId: fk({ to: 'Author', as: 'author', relatedName: 'writtenBooks' }),
            reviewerIds: many({ to: 'Author', as: 'reviewers', relatedName: 'reviewedBooks' })
        };
    }
}

See fk, oneToOne, and many in the documentation for more information.

When declaring model classes, always remember to set the modelName property. It needs to be set explicitly, because running your code through a mangler would otherwise break functionality. The modelName will be used to resolve all related fields.

Declaring modelName:

class Book extends Model {
    static get modelName() {
        return 'Book';
    }
}
// alternative:
Book.modelName = 'Book';

Declaring options:

If you need to specify options to the Redux-ORM database, you can declare a static options property on the Model class with an object key.

// These are the default values.
Book.options = {
    idAttribute: 'id',
    mapName: 'itemsById',
    arrName: 'items',
};

QuerySet

See the full documentation for QuerySet here.

You can access all of these methods straight from a Model class, as if they were class methods on Model. In this case the functions will operate on a QuerySet that includes all the Model instances.

Instance methods:

• toRefArray(): returns the objects represented by the QuerySet as an array of plain JavaScript objects. The objects are direct references to the store.
• toModelArray(): returns the objects represented by the QuerySet as an array of Model instances objects.
• count(): returns the number of Model instances in the QuerySet.
• exists(): return true if number of entities is more than 0, else false.
• filter(filterArg): returns a new QuerySet representing the records from the parent QuerySet that pass the filter. For filterArg, you can either pass an object that Redux-ORM tries to match to the entities, or a function that returns true if you want to have it in the new QuerySet, false if not. The function receives a model instance as its sole argument.
• exclude returns a new QuerySet represeting entities in the parent QuerySet that do not pass the filter. Similarly to filter, you may pass an object for matching (all entities that match will not be in the new QuerySet) or a function. The function receives a model instance as its sole argument.
• all() returns a new QuerySet with the same entities.
• at(index) returns an Model instance at the supplied index in the QuerySet.
• first() returns an Model instance at the 0 index.
• last() returns an Model instance at the querySet.count() - 1 index.
• delete() deleted all entities represented by the QuerySet.
• update(mergeObj) updates all entities represented by the QuerySet based on the supplied object. The object will be merged with each entity.

Session

See the full documentation for Session here

Instantiation:

You don't need to do this yourself. Use orm.session (usually what you want) or orm.mutableSession.

Instance properties:

• state: the current database state in the session.

Additionally, you can access all the registered Models in the schema for querying and updates as properties of this instance. For example, given a schema with Book and Author models,

const session = orm.session(state);
session.Book // Model class: Book
session.Author // Model class: Author
session.Book.create({ id: 5, name: 'Refactoring', release_year: 1999 });

Changelog

API is still unstable. Minor changes before v1.0.0 can and will include breaking changes, adhering to Semantic Versioning.

See CHANGELOG.md.

The 0.9.x versions brought big breaking changes to the API. Please look at the migration guide if you're migrating from earlier versions.

Looking for the 0.8 docs? Read the old README.md in the repo. For the API reference, clone the repo, npm install, make build and open up index.html in your browser. Sorry for the inconvenience.

License

MIT. See LICENSE.