GraphQL

Using Graphql with Overmind gives you the following benefits:

  • Query: The query for data is run with the rest of your application logic, unrelated to mounting components

  • Cache: You integrate the data from Graphql with your existing state, allowing you to control when new data is needed

  • Optimistic updates: With the data integrated with your Overmind state you can also optimistically update that state before running a mutation query

The Graphql package does not support subscriptions currently

Get up and running

Install the separate package:

npm install overmind-graphql

Initial state

The Graphql package is a configuration factory. That means you need some existing configuration before going:

overmind/index.js
overmind/state.js
overmind/index.js
import { state } from './state'
export const config = {
state
}
overmind/state.js
export const state = {
posts: []
}

The factory

Now let us introduce the factory:

overmind/index.js
overmind/queries.js
overmind/mutations.js
overmind/index.js
import { graphql } from 'overmind-graphql'
import * as queries from './queries'
import * as mutations from './mutations'
import { state } from './state'
export const config = graphql({
state
}, {
endpoint: 'http://some-endpoint.dev',
queries,
mutations
})
overmind/queries.js
import { gql } from 'overmind-graphql'
export const posts = gql`
query Posts {
posts {
id
title
}
}
`;
overmind/mutations.js
import { gql } from 'overmind-graphql'
export const createPost = gql`
mutation CreatePost($title: String!) {
createPost(title: $title) {
id
}
}
`

You define queries and mutations as part of the second argument to the factory, with what endpoint you want to connect to. These queries and mutations are converted into Overmind effects that you can call from your actions.

Query

To call a query you will typically use an action. Let us create an action that uses our posts query.

overmind/index.js
overmind/actions.js
overmind/index.js
import { graphql } from 'overmind-graphql'
import * as actions from './actions'
import * as queries from './queries'
import * as mutations from './mutations'
import { state } from './state'
export const config = graphql({
state,
actions
}, {
endpoint: 'http://some-endpoint.dev',
queries,
mutations
})
overmind/actions.js
export const getPosts = async ({ state, effects }) => {
const { posts } = await effects.queries.posts()
state.posts = posts
}

Mutate

Mutation queries are basically the same as normal queries. You would typically also call these from an action.

overmind/actions.js
overmind/actions.js
export const getPosts = async ({ state, effects }) => {
const { posts } = await effects.queries.posts()
state.posts = posts
}
export const addPost = async ({ effects }, title) => {
await effects.mutations.createPost({ title })
}

Cache

Now that we have the data from our query in the state, we can decide ourselves when we want this data to update. It could be related to moving back to a certain page, maybe you want to update the data in the background or maybe it is enough to just grab it once. You do not really think about it any differently here than with any other data fetching solution.

Optimistic updates

Again, since our data is just part of our state we are in complete control of optimistically adding new data. Let us create an optimistic post.

overmind/actions.js
overmind/actions.js
export const getPosts = async ({ state, effects }) => {
const { posts } = await effects.queries.posts()
state.posts = posts
}
export const addPost = async ({ state, effects }, title) => {
const optimisticId = String(Date.now())
state.posts.push({
id: optimisticId,
title
})
const { id } = await effects.mutations.createPost({ title })
const optimisticPost = state.posts.find(post => post.id === optimisticId)
optimisticPost.id = id
}

Options

There are two points of options in the Graphql factory. The headers and the options.

The headers option is a function which receives the state of the application. That means you can produce request headers dynamically. This can be useful related to authentciation.

overmind/index.js
overmind/index.js
import { graphql } from 'overmind-graphql'
import * as queries from './queries'
import * as mutations from './mutations'
import { state } from './state'
export const config = graphql({
state
}, {
endpoint: 'http://some-endpoint.dev',
headers: (state) => ({
authorization: `Bearer ${state.auth.token}`
}),
queries,
mutations
})

The options are the options passed to GRAPHQL-REQUEST.

overmind/index.js
overmind/index.js
import { graphql } from 'overmind-graphql'
import * as queries from './queries'
import * as mutations from './mutations'
import { state } from './state'
export const config = graphql({
state
}, {
endpoint: 'http://some-endpoint.dev',
headers: (state) => ({
authorization: `Bearer ${state.auth.token}`
}),
options: {
credentials: 'include',
mode: 'cors',
},
queries,
mutations
})

Typescript

There is only a single type exposed by the library, Query. It is used for both queries and mutations.

overmind/queries.ts
overmind/queries.ts
import { Query, gql } from 'overmind-graphql'
// You will understand this very soon
import { Posts } from './graphql-types'
export const posts: Query<Posts> = gql`
query Posts {
posts {
id
title
}
}
`;

The first Query argument is the result of the query. There is also a second query argument which is the payload to the query, as seen here.

overmind/mutations.ts
overmind/mutations.ts
import { Query, gql } from 'overmind-graphql'
// You will understand this very soon
import { CreatePost, CreatePostVariables } from './graphql-types'
export const createPost: Query<CreatePost, CreatePostVariables> = gql`
mutation CreatePost($title: String!) {
createPost(title: $title) {
id
}
}
`

Generate typings

It is possible to generate all the typings for the queries and mutations. This is done by using the APOLLO project CLI. Install it with:

npm install apollo --save-dev

Now you can create a script in your package.json file that looks something like:

{
"scripts": {
"schema": "apollo schema:download --endpoint=http://some-endpoint.dev graphql-schema.json && apollo codegen:generate --localSchemaFile=graphql-schema.json --target=typescript --includes=src/overmind/**/*.ts --tagName=gql --no-addTypename --globalTypesFile=src/overmind/graphql-global-types.ts graphql-types"
}
}

To update your types, simply run:

npm run schema

Apollo will look for queries defined with the gql template tag and automatically produce the typings. That means whenever you add, remove or update a query in your code you should run this script to update the typings. It also produces what is called graphql-global-types. These are types related to fields on your queries, which can be used in your state definition and/or actions.

Note that initially you have to define your queries without types and after running the script you can start typing them to get typing in your app and ensure that your app does not break when you change the queries either in the client or on the server

Optimize query

It is possible to transpile the queries from strings into code. This reduces the size of your bundle, though only noticeably if you have a lot of queries. This can be done with the BABEL-PLUGIN-GRAPHQL-TAG.