Apollo Link Ethereum

apollo-link-ethereum allows you to use GraphQL to speak directly to a smart contract on the Ethereum blockchain. The package integrates with Apollo Client as a "link". There are several "resolvers" so that you can resolve web3 calls using either web3js 1.0 or Ethers.js. A separate mutations package is available to actually execute transactions.

| Package | Description | | --- | --- | | apollo-link-ethereum | The base package | | apollo-link-ethereum-resolver-ethersjs | Resolve calls using Ethers.js | | apollo-link-ethereum-mutations-ethersjs | Send transactions with Ethers.js | | apollo-link-ethereum-resolver-web3js | Resolve calls using Web3js 1.0 |

To see a simple read-only app see the apollo-link-ethereum-example. Otherwise, for a more complex application have a look at ZeppelinOS Registry.

Installation

$ yarn add apollo-link-ethereum

You'll need to either install the Ethers.js package or the Web3.js package in order to make calls to Ethereum. Currently the Ethers.js resolver is more robust.

In your app, you'll need to add the EthereumLink to your Apollo Client:

import { EthersResolver } from 'apollo-link-ethereum-resolver-ethersjs'
import { EthereumLink, AbiMapping } from 'apollo-link-ethereum'

export const abiMapping = new AbiMapping()
abiMapping.addAbi('MKR', mkrAbi) // assuming mkrAbi is an ABI
abiMapping.addAddress('MKR', 1, '0x9f8F72aA9304c8B593d555F12eF6589cC3A579A2')

const ethersProvider = new ethers.getDefaultProvider('homestead')

const ethersResolver = new EthersResolver({
  abiMapping,
  ethersProvider
})

const ethereumLink = new EthereumLink(ethersResolver)

export const apolloClient = new ApolloClient({
  cache: new InMemoryCache(),
  link: ethereumLink
})

Reference

EthereumLink

The object that determines whether queries are Ethereum queries or not. It takes a resolver as an argument. You can use either one of the Web3.js or Ethers.js resolvers.

• new EthereumLink(resolverInstance) Creates a new EthereumLink with the given resolver.

AbiMapping

The object that stores the contract names, network addresses, and ABIs.

• AbiMapping#addAbi(contractName, abi) Adds an ABI that can be looked up by the contract name.
• AbiMapping#addAddress(contractName, networkId, address) Adds a network-specific address for a contract name. This is used to automatically find contract addresses given a contract name.