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XDC iOS SDK

Example

To run the example project, clone the repo, and run pod install from the Example directory first.

Requirements

Installation

There are multiple possibilities to install XDC iOS SDK on your project or machine, depending on your needs and preferences.

XDC3Swift is available through CocoaPods. To install it, simply add the following line to your Podfile:

pod 'XDC3Swift'

bash

$ pod install

Ruby

pod 'XDC’

Getting Started

Create an instance of XDCAccount with an XDCKeyStorage provider. This provides a wrapper around your key for use.

Swift

Import XDC3Swift

Creating an XDC Account 

let keyStorage = XDCKeyLocalStorage()
let account = try? XDCAccount.create(keyStorage: keyStorage, keystorePassword: "MY_PASSWORD")

Create an instance of XDCClient. It will provide you access to a set of functions interacting with the blockchain.

guard let clientUrl = URL(string: "https://apothem-or-mainnet-url") else { return }
let client = XDCClient(url: clientUrl)

You can then interact with the client methods, such as to get the current gas price:

client.eth_gasPrice { (error, currentPrice) in
    print("The current gas price is \(currentPrice)")
}

Creating an instance of XRC20

let xdcClient = XRC20.init(client: XDCClient(url: clientUrl!))

Now, we can interact with the XRC20 read methods.

  • name() → string Returns the name of the token.

xdcClient.name(tokenContract: XDCAddress("Token address")) { (err, name) in
                print("Name of token : \(name!)")
        }

Transfer XDC For transferring XDC from one account to another, we must have the private key of the sender's address.

let account = try! XDCAccount.init(keyStorage: XDCPrivateKeyStore(privateKey: "privateKey"))

We need to create an instance of XDCTransaction with values we want to send to the account.

let tx = XDCTransaction(from: nil, to: XDCAddress(xdcAddress), value: BigUInt(value), data: nil, nonce: 3, gasPrice: BigUInt(4000004), gasLimit: BigUInt(50005), chainId: 51)

Now, we need to call the eth_sendRawTransaction method.

client.eth_sendRawTransaction(tx, withAccount: self.account!) { (err, tx) in
     print(tx ?? "no tx")

We will receive one txHash which will include all data of the transaction.

Data types

The library provides some types and helpers to make interacting with web3 and Ethereum easier.

  • XDCAddress: For the representation of addresses, including checksum support.

  • BigInt and BigUInt: Using [BigInt](https://github.com/attaswift/BigInt) library

  • XDCBlock: Represents the block, either number of RPC-specific definitions like 'Earliest' or 'Latest'

  • XDCTransaction: Wraps a transaction. Encoders and decoders can work with it to generate proper data fields.

Conversion from and to Foundation types

All extensions are namespaced under <type>.web3. So for example, to convert an Int to a hex string:1let str = 100 2let xdcstr = str.web3.xdcString

Supported conversions:

  • Convert from hex byte string ("0xabc") to `Data`

  • Convert from hex byte string ("0xabc") to `Int`

  • Convert from hex byte string ("0xabc") to `BigUInt`

  • Convert String, Int, BigUInt, Data to a hex byte string ("0xabc")

  • Add or remove ‘xdc’ prefixes when working with `String`

XRC20

We support querying XRC20 token data via the `XRC20` struct. Calls allow to:

  • name()

  • symbol()

  • decimals()

  • totalSupply()

  • balanceOf()

  • transfer()

  • transferFrom()

  • approve()

  • allowance()

Dependencies

We built this to be as lightweight as possible. However, there's a couple of reliable C libraries you will find packaged with this framework:

We also use Apple's own CommonCrypto (via GitHub - sergejp/CommonCrypto: CommonCrypto module wrapper project for Xcode 8 and Swift 3 method) and BigInt (GitHub - attaswift/BigInt: Arbitrary-precision arithmetic in pure Swift) via CocoaPod dependency.

XRC20 Token Integration

  • An XRC20 token is a blockchain-based asset with similar functionalities to ether; it can hold value and be sent and received.

  • XRC20 tokens are stored and transferred using XDC addresses and transactions. It uses gas to cover transaction fees.

XRC20 Token

Read methods

name() → string Returns the name of the token.

symbol() → string Returns the symbol of the token, usually a shorter version of the name.

decimals() → uint8 Returns the number of decimals used to get its user representation. For example, if decimal equals 2, a balance of 505 tokens should be displayed to a user as 5,05 (505 / 10 ** 2). Tokens usually opt for a value of 18, imitating the relationship between Ether and Wei.

totalSupply() → uint256 Returns the number of tokens in existence.

balanceOf(address account) → uint256 Returns the number of tokens owned by the account.

allowance(address owner, address spender) → uint256 Returns the remaining number of tokens that the spender will be allowed to spend on behalf of the owner through transferFrom. It is zero by default.

Write methods

approve(address spender, uint256 amount) Sets amount as the allowance of spender over the caller’s tokens.

transfer(address recipient, uint256 amount) Moves tokens from the caller’s account to the recipient.

transferFrom(address sender, address recipient, uint256 amount) Moves tokens from sender to recipient using the allowance mechanism. The amount is deducted from the caller’s allowance.

increaseAllowance(address spender, uint256 addedValue) Automatically increases the allowance granted to spender by the caller.

decreaseAllowance(address spender, uint256 addedValue) Automatically decreases the allowance granted to spender by the caller.

XRC721 Token Integration

What is XRC721 Token?

The XRC-721 introduces a standard for NFT. In other words, this type of token is unique and can have a different value than other tokens from the same Smart Contract, which may be due to its age, rarity or even its visual.

All NFTs have a uint256 variable called tokenId. So, for any XRC721 contract, the pair contract address and uint256 tokenId must be globally unique.

Read Methods

name() → string Returns the name of the token.

symbol() → string Returns the symbol of the token, usually a shorter version of the name.

totalSupply() → uint256 Gets the total amount of tokens stored by the contract.

balanceOf(address account) → uint256 Returns the number of NFTs in the owner's account.

ownerOf(tokenId) → address Returns the owner of the NFT specified by tokenId.

tokenURI(uint256 tokenId) → string Returns the URI for a given tokenID. May return an empty string.

tokenByIndex(uint256 index) → uint256 Gets the token ID at a given index of all the tokens in the contract. Reverts if the index is greater or equal to the total number of tokens.

tokenOfOwnerByIndex(address owner, uint256 index) → uint256 Gets the token ID at a given index of the tokens list of the requested owner.

supportInterface(tokenId) → bool Returns true if the contract implements the interface defined by interfaceId.

getApproved(tokenId) → address Gets the approved address for a token ID or zero if no address is set. Reverts if the token ID does not exist.

isApprovedForAll (address owner, address operator) → bool Tells whether an operator is approved by a given owner.

Write methods

transferFrom(address from, address to, uint256 tokenId) Transfers the ownership of a given token ID to another address.

safeTransferFrom(address from, address to, uint256 tokenId) Safely transfers the ownership of a given token ID to another address.

setApprovalForAll(address operator, bool approved) Sets or unsets the approval of a given operator. An operator is allowed to transfer all tokens of the sender on their behalf.

approve(address to, uint256 tokenId) Approves another address to transfer the given token ID. The zero address indicates there is no approved address. There can only be one approved address per token at a given time. It can only be called by the token owner or an approved operator.

Every XRC-721 contract must implement the XRC721 and XRC165 interfaces.

XRC721 Standard

/// @notice Count all NFTs assigned to an owner

/// @dev NFTs assigned to the zero address are considered invalid, and this

/// function throws for queries about the zero address.

/// @param _owner An address for whom to query the balance

/// @return The number of NFTs owned by _owner, possibly zero function balanceOf(address _owner) external view returns (uint256);

/// @notice Find the owner of an NFT

/// @dev NFTs assigned to zero address are considered invalid, and queries

/// about them do throw.

/// @param _tokenId The identifier for an NFT

/// @return The address of the owner of the NFT function ownerOf(uint256 _tokenId) external view returns (address);

/// @notice Transfers the ownership of an NFT from one address to another address

/// @dev Throws unless msg.sender is the current owner, an authorized

/// operator, or the approved address for this NFT. Throws if _from is

/// not the current owner. Throws if _to is the zero address. Throws if

/// _tokenId is not a valid NFT. When transfer is complete, this function

/// checks if _to is a smart contract (code size > 0). If so, it calls

/// onERC721Received on _to and throws if the return value is not

///bytes4(keccak256("onERC721Received(address,address,uint256,bytes)"))

/// @param _from The current owner of the NFT

/// @param _to The new owner /// @param _tokenId The NFT to transfer

/// @param data Additional data with no specified format, sent in call to _to function safeTransferFrom(address _from, address _to, uint256 _tokenId, bytes data) external payable;

/// @notice Transfers the ownership of an NFT from one address to another address /// @dev This works identically to the other function with an extra data parameter, /// except this function just sets data to "".

/// @param _from The current owner of the NFT

/// @param _to The new owner

/// @param _tokenId The NFT to transfer function safeTransferFrom(address _from, address _to, uint256 _tokenId) external payable;

/// @notice Transfer ownership of an NFT -- THE CALLER IS RESPONSIBLE

/// TO CONFIRM THAT _to IS CAPABLE OF RECEIVING NFTS OR ELSE

/// THEY MAY BE PERMANENTLY LOST

/// @dev Throws unless msg.sender is the current owner, an authorized

/// operator, or the approved address for this NFT. Throws if _from is

/// not the current owner. Throws if _to is the zero address. Throws if

/// _tokenId is not a valid NFT.

/// @param _from The current owner of the NFT

/// @param _to The new owner

/// @param _tokenId The NFT to transfer function transferFrom(address _from, address _to, uint256 _tokenId) external payable;

/// @notice Change or reaffirm the approved address for an NFT

/// @dev The zero address indicates there is no approved address.

/// Throws unless msg.sender is the current NFT owner, or an authorized

/// operator of the current owner.

/// @param _approved The new approved NFT controller

/// @param _tokenId The NFT to approve function approve(address _approved, uint256 _tokenId) external payable;

/// @notice Enable or disable approval for a third party ("operator") to manage

/// all of msg.sender's assets

/// @dev Emits the ApprovalForAll event. The contract MUST allow

/// multiple operators per owner.

/// @param _operator Address to add to the set of authorized operators

/// @param _approved True if the operator is approved, false to revoke approval function setApprovalForAll(address _operator, bool _approved) external;

/// @notice Get the approved address for a single NFT

/// @dev Throws if _tokenId is not a valid NFT.

/// @param _tokenId The NFT to find the approved address for

/// @return The approved address for this NFT, or the zero address if there is none function getApproved(uint256 _tokenId) external view returns (address);

/// @notice Query if an address is an authorized operator for another address

/// @param _owner The address that owns the NFTs

/// @param _operator The address that acts on behalf of the owner

/// @return True if _operator is an approved operator for _owner, false otherwise function isApprovedForAll(address _owner, address _operator) external view returns (bool); }

interface XRC165 {

/// @notice Query if a contract implements an interface

/// @param interfaceID The interface identifier, as specified in ERC-165

/// @dev Interface identification is specified in ERC-165. This function

/// uses less than 30,000 gas.

/// @return true if the contract implements interfaceID and

/// interfaceID is not 0xffffffff, false otherwisefunction supportsInterface(bytes4 interfaceID) external view returns (bool);

}

XRC721 Metadata

@notice An abbreviated name for NFTs in this contract function name() external view returns (string _name);

@notice A descriptive name for a collection of NFTs in this contract function symbol() external view returns (string _symbol);

/// @notice A distinct Uniform Resource Identifier (URI) for a given asset.

/// @dev Throws if _tokenId is not a valid NFT. URIs are defined in RFC

/// 3986. The URI may point to a JSON file that conforms to the "ERC721

/// Metadata JSON Schema". function tokenURI(uint256 _tokenId) external view returns (string);

XRC721 Enumerable

/// @notice Count NFTs tracked by this contract

/// @return A count of valid NFTs tracked by this contract, where each one of

/// them has an assigned and queryable owner not equal to the zero address function totalSupply() external view returns (uint256);

/// @notice Enumerate valid NFTs

/// @dev Throws if _index >= totalSupply().

/// @param _index A counter less than totalSupply()

/// @return The token identifier for the _indexth NFT,

/// (sort order not specified) function tokenByIndex(uint256 _index) external view returns (uint256);

/// @notice Enumerate NFTs assigned to an owner

/// @dev Throws if _index >= balanceOf(_owner) or if

/// _owner is the zero address, representing invalid NFTs.

/// @param _owner An address where we are interested in NFTs owned by them

/// @param _index A counter less than balanceOf(_owner)

/// @return The token identifier for the _indexth NFT assigned to _owner,

/// (sort order not specified) function tokenOfOwnerByIndex(address _owner, uint256 _index) external view returns (uint256);

For calling XRC721 read methods

 var client: XDCClient!
    var xrc721: XRC721!
    var xrc721Metadata : XRC721Metadata!
    var xrc721Enumerable : XRC721Enumerable!
    
    self.client = XDCClient(url: URL(string: "rpc url")!)
    self.xrc721 = XRC721(client: client)
    self.xrc721Metadata = XRC721Metadata(client: client)
    self.xrc721Enumerable = XRC721Enumerable(client: client)

  • To call the name of the token

xrc721Metadata.name(contract: address) { (error, name) in print(name) }

  • To call totalSupply of token

xrc721Enumerable.totalSupply(contract: address) { (error, supply) in print(supply) }

For using XRC721 write methods

We need to have the private key of the owner to perform write methods. We need to create an instance of XDCAccount to use our private key.

let account = try! XDCAccount.init(keyStorage: XDCPrivateKeyStore(privateKey: "your private key"))

safeTransferFrom: It will change ownership of the token.

let function = XRC721Functions.safeTransferFrom(contract: XDCAddress("tokenAddress"), sender: XDCAddress("senderAddress"), to: XDCAddress("toAddress"), tokenId: tokenId)
        let transaction = try? function.transaction(gasPrice: 3500000, gasLimit: 3000000)
        self.client.eth_sendRawTransaction(transaction!, withAccount: self.account!) { (err, txhash) in
            print(txhash!)
    }

It will return a transaction hash that contains the details of the transaction.

Author

XDCFoundation, XFLW@xinfin.org

License

XDC3Swift is available under the MIT license. See the LICENSE file for more info.

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