Use MetaMask SDK with iOS

You can import MetaMask SDK into your native iOS dapp to enable your users to easily connect with their MetaMask Mobile wallet.

Prerequisites

An iOS project set up with iOS version 14+.

Steps

1. Install the SDK

To add the SDK as a Swift Package Manager (SPM) package to your project, in Xcode, select File > Swift Packages > Add Package Dependency. Enter the URL of the MetaMask iOS SDK repository: https://github.com/MetaMask/metamask-ios-sdk.

Alternatively, you can add the URL directly in your project's package file:

dependencies: [
    .package(
        url: "https://github.com/MetaMask/metamask-ios-sdk",
        from: "0.1.0"
    )
]

note

The SDK supports ios-arm64 (iOS devices) and ios-arm64-simulator (M1 chip simulators). It currently doesn't support ios-ax86_64-simulator (Intel chip simulators).

2. Import the SDK

Import the SDK by adding the following line to the top of your project file:

import metamask_ios_sdk

3. Connect your dapp

Connect your dapp by adding the following code to your project file:

@ObservedObject var ethereum = MetaMaskSDK.shared.ethereum

let dapp = Dapp(name: "Dub Dapp", url: "https://dubdapp.com")

// This is the same as calling eth_requestAccounts
ethereum.connect(dapp)

By default, MetaMask logs three SDK events: connectionRequest, connected, and disconnected. This allows MetaMask to monitor any SDK connection issues. To disable this, set MetaMaskSDK.shared.enableDebug = false or ethereum.enableDebug = false.

4. Call provider methods

You can now call any provider API method.

The SDK uses Combine to publish Ethereum events, so you need to define an AnyCancellable storage by adding the following line to your project file:

@State private var cancellables: Set<AnyCancellable> = []

The following examples use the window.ethereum.request(args) provider API method to call various RPC API methods.

Example: Get chain ID

The following example gets the user's chain ID by calling eth_chainId.

@State var chainId: String?

let chainIdRequest = EthereumRequest(method: .ethChainId)

ethereum.request(chainIdRequest)?.sink(receiveCompletion: { completion in
    switch completion {
    case .failure(let error):
        print("\(error.localizedDescription)")
    default: break
    }
}, receiveValue: { result in
    self.chainId = result
})
.store(in: &cancellables)

Example: Get account balance

The following example gets the user's account balance by calling eth_getBalance.

@State var balance: String?

// Create parameters
let parameters: [String] = [
    ethereum.selectedAddress, // address to check for balance
    "latest" // "latest", "earliest" or "pending" (optional)
  ]

// Create request
let getBalanceRequest = EthereumRequest(
    method: .ethGetBalance,
    params: parameters)

// Make request
ethereum.request(getBalanceRequest)?.sink(receiveCompletion: { completion in
    switch completion {
    case .failure(let error):
        print("\(error.localizedDescription)")
    default: break
    }
}, receiveValue: { result in
    self.balance = result
})
.store(in: &cancellables)

Example: Send transaction

The following examples send a transaction by calling eth_sendTransaction.

Use a dictionary

If your request parameters make up a simple dictionary of string key-value pairs, you can use the dictionary directly. Note that Any or even AnyHashable types aren't supported, since the type must be explicitly known.

// Create parameters
let parameters: [String: String] = [
    "to": "0x...", // receiver address
    "from": ethereum.selectedAddress, // sender address
    "value": "0x..." // amount
  ]

// Create request
let transactionRequest = EthereumRequest(
    method: .ethSendTransaction,
    params: [parameters] // eth_sendTransaction expects an array parameters object
    )

// Make a transaction request
ethereum.request(transactionRequest)?.sink(receiveCompletion: { completion in
    switch completion {
    case .failure(let error):
        print("\(error.localizedDescription)")
    default: break
    }
}, receiveValue: { result in
    print(result)
})
.store(in: &cancellables)

Use a struct

For more complex parameter representations, define and use a struct that conforms to CodableData, that is, implements the following requirement:

func socketRepresentation() -> NetworkData

The type can then be represented as a socket packet.

struct Transaction: CodableData {
    let to: String
    let from: String
    let value: String
    let data: String?

    init(to: String, from: String, value: String, data: String? = nil) {
        self.to = to
        self.from = from
        self.value = value
        self.data = data
    }

    func socketRepresentation() -> NetworkData {
        [
            "to": to,
            "from": from,
            "value": value,
            "data": data
        ]
    }
}

// Create parameters
let transaction = Transaction(
    to: "0x...", // receiver address
    from: ethereum.selectedAddress, // sender address
    value: "0x..." // amount
)

// Create request
let transactionRequest = EthereumRequest(
    method: .ethSendTransaction,
    params: [transaction] // eth_sendTransaction expects an array parameters object
    )

// Make a transaction request
ethereum.request(transactionRequest)?.sink(receiveCompletion: { completion in
    switch completion {
    case .failure(let error):
        print("\(error.localizedDescription)")
    default: break
    }
}, receiveValue: { result in
    print(result)
})
.store(in: &cancellables)