next.js/examples/with-mobx

MobX example

How to use

Using create-next-app

Execute create-next-app with Yarn or npx to bootstrap the example:

npx create-next-app --example with-mobx with-mobx-app
# or
yarn create next-app --example with-mobx with-mobx-app

Download manually

Download the example:

curl https://codeload.github.com/zeit/next.js/tar.gz/canary | tar -xz --strip=2 next.js-canary/examples/with-mobx
cd with-mobx

Install it and run:

npm install
npm run dev
# or
yarn
yarn dev

Deploy it to the cloud with now (download)

now

Notes

This example is a mobx port of the with-redux example. Decorator support is activated by adding a .babelrc file at the root of the project:

{
  "presets": [
    "next/babel"
  ],
  "plugins": [
    ["@babel/plugin-proposal-decorators", { "legacy": true }],
    ["@babel/plugin-proposal-class-properties", { "loose": true }]
  ]
}

Rehydrating with server data

Be aware that data that was used on the server (and provided via getInitialProps) will be stringified in order to rehydrate the client with it. That means, if you create a store that is, say, an ObservableMap and give it as prop to a page, then the server will render appropriately. But stringifying it for the client will turn the ObservableMap to an ordinary JavaScript object (which does not have Map-style methods and is not an observable). So it is better to create the store as a normal object and turn it into a Observable in the render() method. This way both sides have an Observable to work with.

The idea behind the example

Usually splitting your app state into pages feels natural but sometimes you'll want to have global state for your app. This is an example on how you can use mobx that also works with our universal rendering approach. This is just a way you can do it but it's not the only one.

In this example we are going to display a digital clock that updates every second. The first render is happening in the server and then the browser will take over. To illustrate this, the server rendered clock will have a different background color than the client one.

Our page is located at pages/index.js so it will map the route /. To get the initial data for rendering we are implementing the static method getInitialProps, initializing the mobx store and returning the initial timestamp to be rendered. The root component for the render method is the mobx-react Provider that allows us to send the store down to children components so they can access to the state when required.

To pass the initial timestamp from the server to the client we pass it as a prop called lastUpdate so then it's available when the client takes over.

The trick here for supporting universal mobx is to separate the cases for the client and the server. When we are on the server we want to create a new store every time, otherwise different users data will be mixed up. If we are in the client we want to use always the same store. That's what we accomplish on store.js

The clock, under components/Clock.js, has access to the state using the inject and observer functions from mobx-react. In this case Clock is a direct child from the page but it could be deep down the render tree.