swift-ethereum

The Ethereum Swift library to connect Ethereum JSON-RPC API and interact with Ethereum data structures.

Features

• 🚧 Basic Ethereum entity definitions
• 🚧 Interact with Smart Contracts by Swifty interface
  • Currenty, supports only ERC20
• ✅ ABI encoding & decoding with Codable-like interface

Usage

Interacts with Smart Contracts

Initialize contract interface

let address = Address(hexString: "0x<contract address>")
let provider = JSONRPCProvider(
    rpcURL: URL(string: "https://<your JSON RPC URL>"),
    session: .shared
)
let contract = ERC20(contract: address, provider: provider)

Call view functions

The example to call ERC20.balanceOf(address):

let owner = Address(hexString: "0x<owner address>")
let balance = try await contract.balanceOf(owner: owner)
print(balance) // => 123

Send transaction to execute function

This is the example to send transaction to execute ERC20.transfer(address,uint256).

First, you need to prepare PrivateKey and Signer objects.

Signer represents the signing methods of the blockchain. Currently, swift-ethereum only has LondonSigner which supports to sign for past London update of Ethereum.

let privateKey = try PrivateKey(hexString: "0x<your private key>")
let signer = LondonSigner(chainID: 1)

Then you need to build TransactionOptions object which contains some values to build transaction. PrivateKey and Signer objects you created are needed to pass to TransactionOptions object.

let gWei = BigUInt(10).power(9)
let options = TransactionOptions(
    nonce: 10,
    maxPriorityFeePerGas: 1,
    maxFeePerGas: 30 * gWei,
    gas: 100000,
    signer: signer,
    privateKey: privateKey
)

Finally, you can send transaction through contract interface object. Note that functions which is not marked as view or pure in Solidity will return the hash of tx as a result.

let to = Address(hexString: "0x<to address>")
let value = BigUInt(123)
let txHash = try await contract.transfer(
    to: to,
    value: 123,
    options: options
)
print(txHash) // => Hash of sent transaction

ABI Encoding

You can use ABIDataEncoder/Decoder.

// The parameter of ERC20 balanceOf(address) function.
let parameter = Tuple1(Address(hexString: "0xB9084d9c8A70b8Ecd2b6878ceF735F11b060DE32"))
// Encoding
let encoded = try ABIDataEncoder().encode(parameter)
// Decoding
let decoded = try ABIDataDecoder().decode(Tuple1<Address>.self, from: encoded)

ABIDataEncoder/Decoder accepts the type which conforms ABIEncodable/Decodable. The most of basic entities already conforms to ABIEncodable/Decodable, but you can make custom type conformed to ABIEncodable/Decodable by yourself.

struct Params: ABICodable {
    let address: Address
    let integer: BigInt

    init(from decoder: ABIDecoder) throws {
        var container = decoder.container()
        self.address = try container.decode(Address.self)
        self.integer = try container.decode(BigInt.self)
    }

    func encode(to encoder: ABIEncoder) throws {
        var container = encoder.container()
        try container.encode(address)
        try container.encode(integer)
    }
}

Author

@andooown

License

Apache License Version 2.0

This product includes software developed by the “Marcin Krzyzanowski” (http://krzyzanowskim.com/).