W3Connect

W3Connect is a Swift library for interacting with the blockchain & smart contract ecosystem using the Web3 interface. By connecting to a network or node, you can to compose, send transactions and read values from smart contracts without the need of writing your own implementations of the protocols.

W3Connect aims to make it as simple and easy to follow and understand. The class structure follows the same pattern as the official Web3 library but renames and organizes the classes, variables, and methods for ease of use, efficiency, and understanding.

W3Connect supports all networks that are compatible with the Ethereum web3.js library.

• Ethereum (ETH)
• Binance Smart-Chain (BSC)

Usage

To use the library, add import W3Connect in your swift files.

import W3Connect

Define a new connection with a Provider:

let w3 = Blockchain(connectTo: "https://mainnet.infura.io/<your_infura_id>")

Interaction with an Blockchain node

With W3Connect you can use a local or remote node as the Provider to communicate with the blockchain network allowing for fetching address balances, signing of transactions, reading contracts and calling of contracts and their respective functions.

All standard Web3 web3_ methods are accessible using the base Blockchain struct.

struct Blockchain {
	let network: Network
	let node: Node
	...
}

Network: Provides information about the current connected network and related data. Renamed from net_.

Node: Allows for interacting with the blockchain and it's smart contracts. Renamed from eth_.

Send Raw Transaction

Creates new message call transaction or a contract creation for signed transactions.

Parameters

1. Transaction: The signed transaction

Returns

NetworkData, 32 Bytes - The transaction hash, or the zero hash if the transaction is not yet available

To send some ETH you first need to get the current transaction count of the sender (nonce), create the transaction, sign it and then send it.

let privateKey = try! EthereumPrivateKey(hexPrivateKey: "0xa26da69ed1df3ba4bb2a231d506b711eace012f1bd2571dfbfff9650b03375af")
firstly {
    web3.eth.getTransactionCount(address: privateKey.address, block: .latest)
}.then { nonce in
    let tx = try EthereumTransaction(
        nonce: nonce,
        gasPrice: EthereumQuantity(quantity: 21.gwei),
        gas: 21000,
        to: EthereumAddress(hex: "0xC0866A1a0ed41e1aa75c932cA3c55fad847fd90D", eip55: true),
        value: EthereumQuantity(quantity: 1.eth)
    )
    return try tx.sign(with: privateKey, chainId: 1).promise
}.then { tx in
    web3.eth.sendRawTransaction(transaction: tx)
}.done { hash in
    print(hash)
}.catch { error in
    print(error)
}

Request block transaction count by block number

firstly {
    web3.eth.getBlockTransactionCountByNumber(block: .block(5397389))
}.done { count in
    print(count) // 88
}.catch { error in
    print(error)
}

Contract ABI

StaticContract

A protocol that provides predefined functions and events to interact with the contract

• ERC20Contract: ERC-20 Standard for Tokens
• ERC721Contract: ERC-721 Standard for NFT

DynamicContract

A parsed JSON-RPC object representation that dynamically generates a contract at run-time.

There are several options to create contract abi interfaces:

• Use the generic ERC20 or ERC721 static Contract
• Creating your own Contract interface to make contract calls
• Parse the JSON ABI representation of the dynamic Contract, just like in web3.js

By creating your own interfaces, you can interact with any smart contract!

Static & Dynamic Contract Examples

Installation

Swift Package Manager

To add W3Connect to a Swift Package Manager based project, add the following to your Package.swift files dependencies array.

.package(name: "W3Connect", url: "https://github.com/rkohl/W3Connect", .upToNextMajor(from: "1.1.0")),

Contributors

• Boilertalk/Web3.swift

License

W3Connect is available under the MIT license. See the LICENSE file for more info.