Getting started

In this guide we will demonstrate how to:

1. Connect to the zkSync network.
2. Deposit assets from Ethereum into zkSync.
3. Check balances.
4. Transfer and withdraw funds (native and ERC20 tokens).
5. Deploy a smart contract.

Note

This section of the documentation is under review to reflect the changes made to the system contracts (see changelog). A revised version will be available shortly.

Prerequisite

This guide assumes that you are familiar with Swift programming language.

Installation

CocoaPods

CocoaPods is a dependency manager for Cocoa projects. You can install it with the following command:

sudo gem install cocoapods

To integrate zkSync swift SDK into your Xcode project using CocoaPods, specify it in your Podfile:

platform :ios, '13.0'
use_frameworks!

install! 'cocoapods', :warn_for_unused_master_specs_repo => false

target '<Your Target Name>' do
  pod 'ZkSync2', '~> 0.0.1'
end

Then run the following command:

pod install

Connecting to zkSync

To interact with the zkSync network users need to know the endpoint of the operator node.

Create an instance of EthereumAccount with a EthereumKeyStorage provider. This provides a wrapper around your key for web3.swift to use.

NOTE: We recommend you implement your own KeyStorage provider, instead of relying on the provided EthereumKeyLocalStorage class.

import web3

// This is just an example. EthereumKeyLocalStorage should not be used in production code
let keyStorage = EthereumKeyLocalStorage()
let account = try? EthereumAccount.create(replacing: keyStorage, keystorePassword: "MY_PASSWORD")

Create an instance of EthereumHttpClient or EthereumWebSocketClient. This will then provide you access to a set of functions for interacting with the zkSync network.

EthereumHttpClient

guard let clientUrl = URL(string: "https://zksync2-testnet.zksync.dev") else { return }
let client = EthereumHttpClient(url: clientUrl)

OR

EthereumWebSocketClient

guard let clientUrl = URL(string: "wss://zksync2-testnet.zksync.dev/ws") else { return }
let client = EthereumWebSocketClient(url: clientUrl)

You can then interact with the client methods:

approveDeposits

It returns the erc20 token address.

    func approveDeposits(with token: Token,
                         limit: BigUInt?) throws -> Promise<TransactionSendingResult>

Parameters

Name	Description
token	The Ethereum address of the token.
limit(optional)	The maximum amount to approve a zkSync contract.

transfer

The transfer method can transfer ERC20 tokens, and it returns the transaction receipt of the transfer.

    /// Send transfer transaction. This is the regular transfer of ERC20 token.
    /// - Parameters:
    func transfer(with token: Token,
                  amount: BigUInt,
                  to address: String) throws -> Promise<TransactionSendingResult>

Parameter

Name	Description
token	The ERC20 token address.
amount	The amount of tokens to transfer
address	The Tokens receiver address.

deposit

This method uses EthereumProvider.approveDeposits() to send deposit transactions to zkSync contracts and returns the transaction receipt of the deposit.

    func deposit(with token: Token,
                 amount: BigUInt,
                 to userAddress: String) throws -> Promise<TransactionSendingResult>

Parameter

Name	Description
token	The address of the token to deposit.
amount	The amount of the token to be deposited.
userAddress	The address that will receive the deposited tokens on L2.

withdraw

This method send withdrawals to the specified token address and returns the transaction receipt.

    func withdraw(with token: Token,
                  amount: BigUInt,
                  from userAddress: String) throws -> Promise<TransactionSendingResult>

Parameter

Name	Description
token	The address of the token to withdraw.
amount	The amount of the token to withdraw.
userAddress	The L1 withdrawal receiver address in zkSync.

isDepositApproved

This method checks if the deposit is approved and returns a Boolean.

    func isDepositApproved(with token: Token,
                           address: String,
                           threshold: BigUInt?) throws -> Bool

Parameter

Name	Description
token	The address of the token deposited.
address	The amount of the token deposited.
threshold	The minimum threshold of approved tokens.
returns	Boolean value that denotes whether deposit was approved or not.