drizzle

Now it connects also to VeChain!

npm install --save drizzle@npm:drizzle-vechain

Drizzle is a collection of front-end libraries that make writing dapp frontends easier and more predictable. The core of Drizzle is based on a Redux store, so you have access to the spectacular development tools around Redux. We take care of synchronizing your contract data, transaction data and more. Things stay fast because you declare what to keep in sync.

• Fully reactive contract data, including state, events and transactions.
• Declarative, so you're not wasting valuable cycles on uneeded data.
• Maintains access to underlying functionality. Web3 and your contract's methods are still there, untouched.

Using React?: The easiest way to get started with Drizzle is to use our official drizzle-react package and (optionally) its companion drizzle-react-components.

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 { Drizzle } from 'drizzle'

2. Create an options object and pass in the desired contract artifacts for Drizzle to instantiate. Other options are available, see the Options section below.

   // Import contracts
   import SimpleStorage from './../build/contracts/SimpleStorage.json'
   import TutorialToken from './../build/contracts/TutorialToken.json'
   
   const options = {
     contracts: [
       SimpleStorage
     ]
   }
   
   const drizzle = new Drizzle(options)

   Note: The above assumes you have no existing redux store and will generate a new one. If you need something more sophisticated, consult our documentation Using Drizzle's Redux Store

3. Get contract data. Calling the cacheCall() function on a contract will execute the desired call and return a corresponding key so the data can be retrieved from the store. When a new block is received, Drizzle will refresh the store automatically if any transactions in the block touched our contract. For more information on how this works, see How Data Stays Fresh.

   Note: We have to check that Drizzle is initialized before fetching data. A simple if statement such as below is fine for displaying a few pieces of data, but a better approach for larger dapps is to use a loading component. We've already built one for you in our drizzle-react-components library as well.

   // Assuming we're observing the store for changes.
   var state = drizzle.store.getState()
   
   // If Drizzle is initialized (and therefore web3, accounts and contracts), continue.
   if (state.drizzleStatus.initialized) {
    // Declare this call to be cached and synchronized. We'll receive the store key for recall.
    const dataKey = drizzle.contracts.SimpleStorage.methods.storedData.cacheCall()
   
    // Use the dataKey to display data from the store.
    return state.contracts.SimpleStorage.storedData[dataKey].value
   }
   
   // If Drizzle isn't initialized, display some loading indication.
   return 'Loading...'

   The contract instance has all of its standard web3 properties and methods. For example, you could still call as normal if you don't want something in the store:

   drizzle.contracts.SimpleStorage.methods.storedData().call()

4. Send a contract transaction. Calling the cacheSend() function on a contract will send the desired transaction and return a corresponding transaction hash so the status can be retrieved from the store. The last argument can optionally be an options object with the typical from, gas and gasPrice keys. Drizzle will update the transaction's state in the store (pending, success, error) and store the transaction receipt. For more information on how this works, see How Data Stays Fresh.

   Note: We have to check that Drizzle is initialized before fetching data. A simple if statement such as below is fine for displaying a few pieces of data, but a better approach for larger dapps is to use a loading component. We've already built one for you in our drizzle-react-components library as well.

   // Assuming we're observing the store for changes.
   var state = drizzle.store.getState()
   
   // If Drizzle is initialized (and therefore web3, accounts and contracts), continue.
   if (state.drizzleStatus.initialized) {
    // Declare this transaction to be observed. We'll receive the stackId for reference.
    const stackId = drizzle.contracts.SimpleStorage.methods.set.cacheSend(2, {from: '0x3f...'})
   
    // Use the dataKey to display the transaction status.
    if (state.transactionStack[stackId]) {
      const txHash = state.transactionStack[stackId]
   
      return state.transactions[txHash].status
    }
   }
   
   // If Drizzle isn't initialized, display some loading indication.
   return 'Loading...'

   For more information on what's contained in transaction state, see Drizzle State.

   The contract instance has all of its standard web3 properties and methods. For example, you could still send as normal if you don't want a tx in the store:

   drizzle.contracts.SimpleStorage.methods.set(2).send({from: '0x3f...'})

Adding contracts dynamically

You can programmatically add contracts to Drizzle using either drizzle.addContract() or the ADD_CONTRACT action.

var contractConfig = {
  contractName: "0x066408929e8d5Ed161e9cAA1876b60e1fBB5DB75",
  web3Contract: new web3.eth.Contract(/* ... */)
}
events = ['Mint']

// Using an action
dispatch({type: 'ADD_CONTRACT', drizzle, contractConfig, events, web3})

// Or using the Drizzle context object
this.context.drizzle.addContract(contractConfig, events)

Deleting contracts

You can also delete contracts using either drizzle.deleteContract() or the DELETE_CONTRACT action.

const contractName = "MyContract"

// Using an action
dispatch({type: 'DELETE_CONTRACT', drizzle, contractName})

// Or using the Drizzle context object
this.context.drizzle.deleteContract(contractName)

Options

Drizzle has a number of configuration options so it only keeps track of exactly the data you need. Here's the full list of options along with their default values.

{
  contracts,
  events: {
    contractName: [
      eventName,
      {
        eventName,
        eventOptions
      }
    ]
  },
  polls: {
    accounts: interval,
    blocks: interval
  },
  syncAlways,
  web3: {
    vechain: true,
    customProvider,
    fallback: {
      type
      url
    }
  },
  networkWhitelist
}

contracts (array)

An array of either contract artifact files or Web3 contract objects. The objects have a contractName and web3Contract key.

i.e.

contracts: [
  truffleArtifact, // A regular Truffle contract artifact
  {
    contractName: 'RegisteredContract',
    web3Contract: new web3.eth.Contract(abi, address, {data: 'deployedBytecode' }) // An instance of a Web3 contract
  }
]

events (object)

An object consisting of contract names each containing an array of strings of the event names we'd like to listen for and sync with the store. Furthermore, event names may be replaced with an object containing both eventName and eventOptions, where eventOptions field corresponds to the web3 Contract.events options.

polls (object)

An object containing key/value pairs denoting what is being polled and the interval (in ms). Possible polls are accounts and blocks. Accounts will poll for addresses and balances, blocks for new blocks. Default: { blocks: 3000 }

syncAlways (boolean)

If true, will replay all contract calls at every block. This is useful if your dapp uses a proxy contract which obfuscates your primary contract's address. By default Drizzle checks blocks to see if a transaction interacting with your contracts has occured. If so, it syncs that contract. Default: false

web3 (object)

Options regarding web3 instantiation.

vechain (string)

Options regarding vechain host definition. Set as true for mainnet.

customProvider (object)

A valid web3 provider object. For example, you may wish to programatically create a Ganache provider for testing:

// Create a Ganache provider.
const testingProvider = Ganache.provider({
  gasLimit: 7000000
})

const options = {
  web3: {
    customProvider: testingProvider
  }
}

const drizzle = new Drizzle(options)

fallback (object)

An object consisting of the type and url of a fallback web3 provider. This is used if no injected provider, such as MetaMask or Mist, is detected.

type (string): The type of the fallback web3 provider. Currently the only possibility is 'ws' (web socket). Default: 'ws'

url (string): The full fallback web3 provider url. Default: 'ws://127.0.0.1:8545'

networkWhitelist (array)

An array of valid network ids for your project. Your smart contracts might only be deployed on particular networks, or you might want to restrict access on networks that are under development.

Allows all networks by default. Ganache bypasses this check and is never restricted.

// Allows the listed networks, plus Ganache
const options = {
  networkWhitelist: [
    1, // Mainnet
    3, // Ropsten
    4, // Rinkeby
    5, // Goerli
    42 // Kovan
  ]
}

Drizzle State

{
  accounts,
  accountBalances: {
    address
  }
  contracts: {
    contractName: {
      initialized,
      synced,
      events,
      callerFunctionName: {
        argsHash: {
          args,
          value
        }
      }
    }
  },
  currentBlock,
  drizzleStatus: {
    initialized
  },
  transactions: {
    txHash: {
      confirmations,
      error,
      receipt,
      status
    }
  },
  transactionStack,
  web3: {
    status
  }
}

accounts (array)

An array of account addresses from web3.

accountBalances (object)

An object whose keys are account addresses and values are account balances (in Wei).

contracts (object)

A series of contract state objects, indexed by the contract name as declared in its ABI.

contractName (object)

initialized (boolean): true once contract is fully instantiated. synced (boolean): false if contract state changes have occurred in a block and Drizzle is re-running its calls.

events (array): An array of event objects. Drizzle will only listen for the events we declared in options.

The contract's state also includes the state of each constant function called on the contract (callerFunctionName). The functions are indexed by name, and contain the outputs indexed by a hash of the arguments passed during the call (argsHash). If no arguments were passed, the hash is 0x0. Drizzle reads from the store for you, so it should be unnecessary to touch this data cache manually.

args (array): Arguments passed to function call. value (mixed): Value returned from function call.

currentBlock (object)

An object the latest block as an object resulting from web3.getBlock(). This is updated once the block is received from a subscription or fetched via polling, but before any processing takes place.

drizzleStatus (object)

An object containing information about the status of Drizzle.

initialized (boolean): true once:

• web3 is found or instantiated
• Account addresses are stored in state
• All contracts are instantiated

initialized (boolean)

false by default, becomes true once a web3 instance is found and the accounts and contracts are fetched.

transactions (object)

A series of transaction objects, indexed by transaction hash.

txHash (object)

confirmations (array): After the initial receipt, further confirmation receipts (up to the 24th). error (object): contains the returned error if any. receipt (object): contains the first transaction receipt received from a transaction's success event.

status (string): true or false depending on transaction status

• pending when the transaction has broadcasted successfully, but is not yet mined
• success when a transaction receipt has been received (you may also wish to check for further confirmations)
• error if any errors occurred after broadcasting

For more in-depth information on the Ethereum transaction lifecycle, check out this great blog post.

transactionStack (array)

In cases where a user cancels a transaction or the transaction is malformed and unable to be broadcasted, it won't receive a hash. To keep track of these cases, a temporary ID will be added to this array and replaced with the transaction hash once broadcasted. The cacheSend() method will return a stackId, which will allow you get the temporary ID to observe this process for your own transaction status indicator UI.

web3 (object)

status (string): initializing, initialized and failed are possible options. Useful for triggering warnings if web3 fails to instantiate.

How Data Stays Fresh

1. Once initialized, Drizzle instantiates web3 and our desired contracts, then observes the chain by subscribing to new block headers.

   

2. Drizzle keeps track of contract calls so it knows what to synchronize.

   

3. When a new block header comes in, Drizzle checks that the block isn't pending, then goes through the transactions looking to see if any of them touched our contracts.

   

4. If they did, we replay the calls already in the store to refresh any potentially altered data. If they didn't we continue with the store data.

   

License

MIT