Redux Migrations

This package is no longer maintained.

A utility for creating redux stores and migrating existing data to the new store's structure.

npm install @yeldirium/redux-migrations
# or
yarn install @yeldirium/redux-migrations

Status

| Category | Status | | ---------------- | ----------------------------------------------------------------------------------------------------------------------------- | | Version | | | Dependencies | | | Dev dependencies | | | Build | | | License | |

Why?

If you use redux to maintain your application's state and persist that state in some way across application starts - be it with a database or a json file - you will at some point run into the problem that your store structure changes. Maybe a new store branch is added or some reducer layers are restructured - migrations are necessary when the persisted state is not usable by a new version of the application anymore.

How?

This project draws inspiration from a migration solutions like doctrine migrations in the way it tracks executed migrations. It adds a store branch for migrations to your applications store (which you cannot modify) in which it keeps track of the ids of executed migrations, so that only new ones are executed.

Migrations will never run multiple times and redux-migrations will tell you if your migration definitions don't match the persisted state.

Use it like so:

const { createStore } = require("redux");
const { migrations } = require("redux-migrations");

const reducer = require("...your reducer");
const fetchStateFromSomewhere = require("...wherever you persist your state");

const migrationDefinitons = [
  {
    id: "12345",
    migrate: state => ({
      ...state,
      newBranch: []
    })
  },
  {
    id: "4895",
    migrate: ({ newBranch, ...restState }) => ({
      ...restState,
      nested: {
        newBranch,
        anotherNewBranch
      }
    })
  }
];

const preloadedState = await fetchStateFromSomewhere();

const store = createStore(
  reducer,
  preloadedState,
  migrations(migrationDefinitions)
);

After all that, the migrations are executed on the preloaded state (if they haven't been before) and the state in the newly created store should have the form you want.

API

migrations(...migrationDefinition): Enhancer

Takes a list of migrations definitions of the form

const migrationDefinition = {
  // Some string identifier. choose it however you like. timestamps or uuids are recommended
  id: "1234",
  migrate: state => {
    return modifyState(state);
  }
};

and returns a redux enhancer.