HzQL

Data Fetching for React Using Horizon 2

npm install --save hzql

• Easy bindings from Horizon into React
• Support for Horizon 2
• Support for server side rendering

HzQL with React colocates your data and components. It requires Horizon 2 for its new hz.model query.

Example

import React, { Component } from 'react'
import { render } from 'react-dom'
import Horizon from '@horizon/client'
import { Provider, connect } from 'hzql'

const horizon = new Horizon

@connect(hz => props => ({
  users: hz('users'),
  posts: hz('posts').order('date')
}))
class UserPosts extends Component {
  render () {
    if (!this.props.users || !this.props.posts) return <span>Loading...</span>
    
    return <div>
      <h1>Users:</h1>
      {this.props.users.map(u => <li key={u.id}>u.name</li>)}
      <h1>Posts:</h1>
      {this.props.posts.map(p => <li key={p.id}>p.title</li>)}
    </div>
  }
}

render(<Provider horizon={horizon}>
  <UserPosts />
</Provider>, document.getElementById('root'))

Setting up HzQL

HzQL exports a Provider component to wrap your app in. Any component using a query must be a child of Provider

Example

import React from 'react'
import { Provider } from 'hzql'
import Horizon from '@horizon/client'
import App from './App'

let horizon = new Horizon()

let WrappedApp = () =>
  <Provider horizon={horizon}>
    <App />
  </Provider>

Writing Queries

Queries are a function of the form hz => props => query. A query can use the props from the parent component to write the query. The exported connect function wires up a query to a component. The keys of the query will be passed as props to the immediate child

Example

import React from 'react'
import { connect } from 'hzql'

const App = props =>
  <pre>Users: {<pre>Users: {props.users}</pre>props.users}</pre>

const query = hz => props => ({
  users: hz('post').order('date')
})

export default connect(query)(App)

To run a live query, use connect.live instead of connect Using the new decorator syntax:

import React from 'react'
import { connect } from 'hzql'

@connect.live(hz => props => ({
  users: hz('post').order('date')
}))
export default class App {
  render () {
    return <pre>Users: {this.props.users}</pre>
  }
}

Waiting for Results

If you would prefer for the component to not render at all until the results of the query arrive, you can use connect.await. This will cause your component to always return null from render until the query is finished.

The watching equivalent of this is connect.liveAwait

Example

import React from 'react'
import { connect } from 'hzql'

const App = props =>
  <pre>Users: {this.props.users}</pre>

const query = hz => props => ({
  users: hz('post').order('date')
})

// This will render to `null` until `hz('posts').order('date')` is retrieved
export default connect.await(query)(App)

Mutations

The horizon instance is passed down to child components, which can perform mutations.

Example

import React, { Component } from 'react'
import { connect } from 'hzql'

class App extends Component {
  constructor (props) {
    super(props)

    this.state = { input: '' }

    this.handleInput = this.handleInput.bind(this)
    this.handleSubmit = this.handleSubmit.bind(this)
  }

  handleInput (e) {
    this.setState({ input: e.target.value })
  }

  handleSubmit () {
    this.props.horizon('posts').store({ message: this.state.input })
  }

  render () {
    return <div>
      <input onChange={this.handleInput} value={this.state.input} />
      <button onClick={this.handleSubmit}>Submit</button>
    </div>
  }
}

export default connect(App)(hz => props => ({}))

Server side rendering

To render on the server, install node-fibers using

npm i -S node-fibers

In your server code, your call to renderToString should look something like

import React from 'react'
import { renderToString } from 'react-dom/server'
import Fiber from 'fibers'
import ws from 'ws'
import Horizon from '@horizon/client'
import { Provider } from 'hzql'
import express from 'express'
import App from './App'

// Give Horizon a websocket library to use
global.WebSocket = ws
const app = express()

app.get('/', () => {
  let hz = new Horizon({ host: 'localhost:8181' })
  
  // Wrap your call to `renderToString` with a Fiber
  Fiber(() => {
  
    // Pass the horizon instance into provider like normal
    // Make sure to pass the `Fiber` library into `Provider` so it
    // knows to use it
    let html = renderToString(<Provider horizon={hz} fiber={Fiber}>
      <App />
    </Provider>)
    
    let cache = hz.$__hzql_cache_string

    res.status(200).send(`
      <html>
        <head>
          <script>window.$HZ_CACHE = ${JSON.stringify(cache)}</script>
        </head>
        <body>
          <div id="root">${html}</div>
        </body>
      </html>
    `)
    
    // On the client, create your provider component like <Provider horizon={horizon} cache={window.$HZ_CACHE}>
  
    // Make sure to disconnect or the server won't stop
    hz.disconnect()
  }).run()
  // Run the Fiber
})

app.listen()