Elixir Ethers

Ethers is a comprehensive Web3 library for interacting with smart contracts on the Ethereum (Or any EVM based blockchain) using Elixir.

Inspired by ethers.js and web3.js, Ethers leverages Elixir's amazing meta-programming capabilities to generate Elixir modules for give smart contracts from their ABI. It also generates beautiful documentation for those modules which can further help developers.

Installation

You can install the package by adding ethers to the list of dependencies in your mix.exs file:

def deps do
  [
    {:ethers, "~> 0.1.0"}
  ]
end

The complete documentation is available on hexdocs.

Configuration

To use Elixir Ethers, ensure you have a configured JSON-RPC endpoint. Configure the endpoint using the following configuration parameter.

# config.exs
config :ethers,
  rpc_client: Ethereumex.HttpClient, # Defaults to: Ethereumex.HttpClient
  keccak_module: ExKeccak, # Defaults to: ExKeccak
  json_module: Jason # Defaults to: Jason

# If using Ethereumex, you need to specify a JSON-RPC server url here
config :ethereumex,
  url: "[URL_HERE]",
  http_headers: [{"Content-Type", "application/json"}]

You can use one of the RPC URLs for your chain/wallet of choice or try out one of them from chainlist.org.

For more configuration options, refer to ethereumex.

To send transactions, you need a wallet client capable of signing transactions and exposing a JSON-RPC endpoint.

Usage

To use Elixir Ethers, you must have your contract's ABI in json format, which can be obtained from etherscan.io. This library also contains standard contract interfaces such as ERC20, ERC721 and some more by default (refer to built-in contracts in hexdocs).

Create a module for your contract as follows:

defmodule MyERC20Token do
  use Ethers.Contract,
    abi_file: "path/to/abi.json",
    default_address: "[Contract address here (optional)]"

  # You can also add more code here in this module if you wish
end

Calling contract functions

After defining the module, all the functions can be called like any other Elixir module.

To fetch the results (return value(s)) of a function you can pass your function result to the Ethers.call/2 function.

# Calling functions on the blockchain
iex> MyERC20Token.balance_of("0x[Address]") |> Ethers.call()
{:ok, 654294510138460920346}

Refer to Ethers.call/2 for more information.

Sending transaction

To send transaction (eth_sendTransaction) to the blockchain, you can use the Ethers.send/2 function.

Ensure that you specify a from option to inform your client which account to use as the signer:

iex> MyERC20Token.transfer("0x[Recipient]", 1000) |> Ethers.send(from: "0x[Sender]")
{:ok, "0xf313ff7ff54c6db80ad44c3ad58f72ff0fea7ce88e5e9304991ebd35a6e76000"}

Refer to Ethers.send/2 for more information.

Getting Logs (Events)

Ethers provides functionality for creating event filters and fetching related events from the blockchain. Each contract generated by Ethers also will have EventFilters module (e.g. MyERC20Token.EventFilters) that can be used to create filters for events.

To create an event filter and then use Ethers.get_logs/2 function like the below example.

# Create The Event Filter
# (`nil` can be used for a parameter in EventFilters functions to indicate no filtering)
iex> filter = MyERC20Token.EventFilters.transfer("0x[From Address Here]", nil)

# Then you can simply list the logs using `Ethers.get_logs/2`

iex> Ethers.get_logs(filter)
{:ok,
 [
   %Ethers.Event{
     address: "0x5883c66ca442461d406f330775d42954bfcf7d92",
     block_hash: "0x83de67fd285067b838790406ea68f21a3afbc0ade534047725b5ccfb904c9ed3",
     block_number: 17077047,
     topics: ["Transfer(address,address,uint256)",
      "0x6b75d8af000000e20b7a7ddf000ba900b4009a80",
      "0x230507f6a391ae5ac0ec124f1c5b8ce454fe3f3d"],
     topics_raw: ["0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef",
      "0x0000000000000000000000006b75d8af000000e20b7a7ddf000ba900b4009a80",
      "0x000000000000000000000000230507f6a391ae5ac0ec124f1c5b8ce454fe3f3d"],
     transaction_hash: "0xaa6fb2e1bbb27f667e76b03e8cde23db694207e06b9aa810d4c20c1f109a58e5",
     transaction_index: 0,
     data: [761112156078097834180608],
     log_index: 0,
     removed: false
   },
   %Ethers.Event{...},
    ...
 ]}

Resolving Ethereum names (ENS domains) using Ethers

To resolve ENS or any other name service provider (which are ENS compatible) in the blockchain you can simply use Ethers.NameService module.

iex> Ethers.NameService.resolve("vitalik.eth")
{:ok, "0xd8da6bf26964af9d7eed9e03e53415d37aa96045"}

Built-in contract interfaces in Ethers

Ethers already includes some of the well-known contract interface standards for you to use. Here is a list of them.

• ERC20 - The well know fungible token standard
• ERC721 - Non-Fungible tokens (NFTs) standard
• ERC777 - Improved fungible token standard
• ERC1155 - Multi-Token standard (Fungible, Non-Fungible or Semi-Fungible)
• Multicall - Multicall3

To use them you just need to specify the target contract address (:to option) of your token and call the functions. Example:

iex> tx_data = Ethers.Contracts.ERC20.balance_of("0x[Holder Address]")
#Ethers.TxData<
  function balanceOf(
    address _owner "0x[Holder Address]"
  ) view returns (
    uint256 balance
  )
>

iex> Ethers.call(tx_data, to: "0x[Token Address]")
{:ok, 123456}

Documentation

For a detailed documentation visit Ethers hexdocs page.

Generated documentation for functions and event filters

Ethers generates documentation for all the functions and event filters based on the ABI data. To get the documentation you can either use the h/1 IEx helper function or generate HTML/epub docs using ExDoc.

Get the documentation of a contract function

iex(3)> h MyERC20Token.balance_of

                             def balance_of(owner)

  @spec balance_of(Ethers.Types.t_address()) :: Ethers.TxData.t()

Prepares balanceOf(address _owner) call parameters on the contract.

This function should only be called for result and never in a transaction on
its own. (Use Ethers.call/2)

State mutability: view

## Function Parameter Types

  • _owner: `:address`

## Return Types (when called with `Ethers.call/2`)

  • balance: {:uint, 256}

Inspecting TxData and EventFilter structs

One cool and potentially useful feature of Ethers is how you can inspect the call

Get the documentation of a event filter

iex(4)> h MyERC20Token.EventFilters.transfer

                             def transfer(from, to)

  @spec transfer(Ethers.Types.t_address(), Ethers.Types.t_address()) ::
          Ethers.EventFilter.t()

Create event filter for Transfer(address from, address to, uint256 value)

For each indexed parameter you can either pass in the value you want to filter
or nil if you don't want to filter.

## Parameter Types (Event indexed topics)

  • from: :address
  • to: :address

## Event `data` Types (when called with `Ethers.get_logs/2`)

These are non-indexed topics (often referred to as data) of the event log.

  • value: {:uint, 256}

Contributing

All contributions are very welcome (as simple as fixing typos). Please feel free to open issues and push Pull Requests. Just remember to be respectful to everyone!

To run the tests locally, you need to run ganache. After installing ganache, just run the following in a new window the you can run the tests on the same machine.

> ganache --wallet.deterministic

Acknowledgements

Ethers was possible to make thanks to the great contributors of the following libraries.

• ABI
• Ethereumex
• ExKeccak

And also all the people who contributed to this project in any ways.

License

Apache License 2.0