React Integration

drizzle-react is the official way to integrate Drizzle with your React dapp.

Check out the Drizzle Truffle Box for a complete example (also featuring drizzle-react-components), or continue reading to create your own setup.

 Installation

Install Drizzle React Components via npm:

npm install --save drizzle-react

Note: drizzle-react requires Requires React 0.14 or greater. You'll also need the drizzle package, if it isn't already installed.

 Getting Started

Note: Since Drizzle uses web3 1.0 and web sockets, be sure your development environment can support these.

  1. Import the provider.

    import { DrizzleProvider } from 'drizzle-react'
    
  2. Create an options object and pass in the desired contract artifacts for Drizzle to instantiate. Other options are available, see the Options section of the Drizzle docs below.

    // Import contracts
    import SimpleStorage from './../build/contracts/SimpleStorage.json'
    import TutorialToken from './../build/contracts/TutorialToken.json'
    
    const options = {
      contracts: [
        SimpleStorage,
        TutorialToken
      ]
    }
    
  3. Wrap your app with DrizzleProvider and pass in an options object.

    <DrizzleProvider options={options}>
      <App />
    </DrizzleProvider>
    
  4. Wrap your components using the drizzleConnect function. It has the same API as the connect() function in react-redux. See their docs here.

    import { drizzleConnect } from 'drizzle-react'
    
    const mapStateToProps = state => {
      return {
        drizzleStatus: state.drizzleStatus,
        SimpleStorage: state.contracts.SimpleStorage
      }
    }
    
    const HomeContainer = drizzleConnect(Home, mapStateToProps);
    

    See Drizzle State in the Drizzle docs for the entire state tree.

  5. Get contract data by accessing the contracts via context. Calling the data() function on a contract will first check the store for a cached result. If empty, Drizzle will query the blockchain and cache the response for future use. For more information on how this works, see How Data Stays Fresh in the Drizzle docs.

    Note: We have to check that Drizzle is initialized before fetching data. A one-liner such as below is fine for display a few pieces of data, but a better approach for larger dapps is to use a loading component.

    // For convenience
    constructor(props, context) {
      super(props)
    
      this.contracts = context.drizzle.contracts
    }
    
    // If Drizzle is initialized (and therefore web3, accounts and contracts), fetch data.
    // This will update automatically when the contract state is altered.
    var storedData = this.props.drizzleStatus.initialized ? this.contracts.SimpleStorage.methods.storedData.data() : 'Loading...'
    

    The contract instance has all of its standard web3 properties and methods. For example, sending a transaction is done as normal:

    this.contracts.SimpleStorage.methods.set(this.state.storageAmount).send()
    

 Recipe: Loading Component

The following wrapper and component will detect when your dapp isn't ready and allow you to display the appropriate status or course of action:

LoadingContainer.js

import Loading from './Loading.js'
import { drizzleConnect } from 'drizzle-react'

// May still need this even with data function to refresh component on updates for this contract.
const mapStateToProps = state => {
  return {
    drizzleStatus: state.drizzleStatus,
    web3: state.web3
  }
}

const LoadingContainer = drizzleConnect(Loading, mapStateToProps);

export default LoadingContainer

Loading.js

import React, { Component, Children } from 'react'

class Loading extends Component {
  constructor(props, context) {
    super(props)
  }

  render() {
    if (this.props.web3.status === 'failed')
    {
      return(
        // Display a web3 warning.
        <main>
          <h1>⚠️</h1>
          <p>This browser has no connection to the Ethereum network. Please use the Chrome/FireFox extension MetaMask, or dedicated Ethereum browsers Mist or Parity.</p>
        </main>
      )
    }

    if (this.props.drizzleStatus.initialized)
    {
      // Load the dapp.
      return Children.only(this.props.children)
    }

    return(
      // Display a loading indicator.
      <main>
        <h1>⚙️</h1>
        <p>Loading dapp...</p>
      </main>
    )
  }
}

export default Loading