Ethereum ERC20 Manipulations in Ruby

This small Ruby gem makes manipulations with Ethereum tokens as simple as possible, when you have a provider of JSON-RPC and WebSockets Ethereum APIs, such as Infura, GetBlock, or Alchemy.

Install it like this:

gem install erc20

Or simply add this to your Gemfile:

gem 'erc20'

Then, make an instance of the main class and use to read balances, send and receive payments:

# Create a wallet:
require 'erc20'
w = ERC20::Wallet.new(
  contract: ERC20::Wallet.USDT, # hex of it
  host: 'mainnet.infura.io',
  http_path: '/v3/<your-infura-key>',
  ws_path: '/ws/v3/<your-infura-key>',
  log: $stdout
)

# Check how many ERC20 tokens are on the given address:
usdt = w.balance(address)

# Send a few ERC20 tokens to someone and get transaction hash:
hex = w.pay(private_key, to_address, amount)

# Stay waiting, and trigger the block when new ERC20 payments show up:
addresses = ['0x...', '0x...'] # only wait for payments to these addresses
w.accept(addresses) do |event|
  puts event[:txn] # hash of transaction
  puts event[:amount] # how much, in tokens (1000000 = $1 USDT)
  puts event[:from] # who sent the payment
  puts event[:to] # who was the receiver
end

You can also check ETH balance and send ETH transactions:

# Check how many ETHs are on the given address:
eth = w.eth_balance(address)

# Send a few ETHs to someone and get transaction hash:
hex = w.eth_pay(private_key, to_address, amount)

To check the price of a gas unit and the expected cost of a payment:

# How many gas units required to send this payment:
units = w.gas_estimate(from, to, amount)

# What is the price of a gas unit, in gwei:
gwei = w.gas_price

To generate a new private key, use eth:

require 'eth'
key = Eth::Key.new.private_hex

To convert a private key to a public address:

public_hex = Eth::Key.new(priv: key).address

To connect to the server via HTTP proxy with basic authentication:

w = ERC20::Wallet.new(
  host: 'go.getblock.io',
  http_path: '/<your-rpc-getblock-key>',
  ws_path: '/<your-ws-getblock-key>',
  proxy: 'http://jeffrey:swordfish@example.com:3128' # here!
)

You can use squid-proxy image to set up your own HTTP proxy server.

Of course, this library works with Polygon, Optimism, and other EVM compatible blockchains.

How to use in command line

This gem also provides a command line tool for sending ETH and ERC20 payments and checking balances.

First, you install it, via gem:

gem install erc20

Then, run it:

erc20 --help

Usage should be straightforward. If you have questions, please submit an issue.

How to use in tests

You can use the ERC20::FakeWallet class that behaves exactly like ERC20::Wallet, but doesn't make any network connections to the provider. Additionally, it records all requests sent to it:

require 'erc20'
w = ERC20::FakeWallet.new
w.pay(priv, address, 42_000)
assert w.history.include?({ method: :pay, priv:, address:, amount: 42_000 })

How to contribute

Read these guidelines. Make sure your build is green before you contribute your pull request. You will need to have Ruby 3.2+ and Bundler installed. Then:

bundle update
bundle exec rake

If it's clean and you don't see any error messages, submit your pull request.