What's New

Release 0.0.3


What's Changed

  • Add Encoder and Decoders for Hex and EthAddress by @hayesgm in #27

Full Changelog: 0.0.2...0.0.3


A lightweight Ethereum library in Swift.

Running Tests

Run the tests using swift test, preferably with xcbeautify:

swift test | xcbeautify

(install xcbeautify via brew install xcbeautify)

For testing with EVM debug information:

swift test -Xswiftc -DDEBUG_EVM



The ABI/Schema enum defines Ethereum ABI definitions and the ABI/Value enum defines an decoded value. You can use quickly encode ABI values using the ABI/Value/encoded computed property:

let data: Data = ABI.Value.tuple1(.array(.string, [.string("hello"), .string("world")])).encoded

and use ABI/Schema/decode(_:) to decode values.

let schema: ABI.Schema = .tuple([.array(.string)])

switch try schema.decode(data) {
case let .tuple1(.array(_, words)):
  print( { $0.asString! }.joined(separator: " and "))
  throw ABI.DecodeError.invalidResponse

As noted above, tuples are generally represented as .tuple2(.uint8(1), .uint8(2)) to make unwrapping easy. You can also unwrap values using helper methods such as ABI/Value/asString, ABI/Value/asBigUInt, ....

Generating Swift from ABI

To generate Swift files from ABI json files (e.g. the out/ directory of forge build), run:

swift run Geno ./out/Cool.sol/Cool.json --outDir Sources/

It's also suggested you run swiftformat on the generated file. See Geno for more information on code generation.


The EVM module allows you to run pure EVM code locally. E.g. if you had the following Solidity file:

// SPDX-License-Identifier: UNLICENSED
pragma solidity ^0.8.13;

contract MyContract {
    function add55(uint256 x) pure external returns (uint256) {
        return 55 + x;

Then, you could grab its deployed bytecode from MyContract.sol/MyContract.json and execute that function in the EVM via EVM/decodeCode(fromData:) and EVM/runQuery(bytecode:query:withValue:):

let code = try! EVM.decodeCode(fromData: Hex.hex("...")) // The deployed bytecode
let result = try! EVM.runQuery(bytecode: code, query: .tuple1(.uint256(22)))
print("result=" + result.asArray![0].asBigUInt!)

Compliance Tests

Compliance tests are Solidity tests which log their results. We then compare the output of the Eth.swift EVM to those results to ensure compliance over a variety of real Solidity contracts.

To build compliance tests, make sure to install forge and install submodules git submodule update --init --recursive and then run ./Tests/Solidity/ Note: you do not need to run this unless you are editing the Compliance tests.

Coding Conventions

Please use swiftformat on all files before checking in. To install swiftformat, run brew install swiftformat.


  • Swift Tools 5.10.0
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Last updated: Thu Jul 04 2024 13:26:20 GMT-0900 (Hawaii-Aleutian Daylight Time)