Generate Calldata for NFT Checkout

Create transaction calldata for NFT purchases

When using OZZOBiT's NFT Checkout feature, you need to generate calldata (encoded function call data) that represents the NFT purchase transaction. This calldata is passed to OZZOBiT so we can execute the purchase on behalf of your user.

What is Calldata?

Calldata is the hex-encoded data that gets sent as part of an Ethereum (or EVM-compatible) transaction. For NFT purchases, it contains the encoded function call to your smart contract's purchase/mint function along with all required parameters.

Generating Calldata

Identify Your Contract's Purchase Function

Determine which function on your smart contract handles purchases. Common patterns include:

Function	Use Case
mint(address to, uint256 amount)	Minting new NFTs
buy(uint256 tokenId)	Purchasing existing NFTs at fixed price
purchase(address buyer, uint256 tokenId)	Marketplace-style purchase
mintWithPrice(address to, uint256 amount, bytes32 proof)	Allowlist minting

Encode the Function Call

Use ethers.js or web3.js to encode the function signature and parameters:

generate-calldata.tstypescript

// Using ethers.js v6
import { ethers } from 'ethers'

async function generateNFTCalldata(
  contractAddress: string,
  functionName: string,
  params: any[]
): Promise<string> {
  // Create contract instance (ABI only needs the target function)
  const abi = [
    `function ${functionName}` // Full ABI fragment with parameter types
  ]
  
  const contract = new ethers.Contract(contractAddress, abi)
  
  // Encode the function call
  const calldata = await contract[functionName].encodeFunctionData(...params)
  
  return calldata
}

// Example: Fixed price mint
const calldata = await generateNFTCalldata(
  '0xYourContractAddress...',   // Your verified NFT contract
  'mint(address,uint256)',       // Function signature
  [
    '0xUserWalletAddress...',    // Recipient address
    1                            // Quantity
  ]
)

console.log('Calldata:', calldata)
// Output: 0xa0712d680000000000... (hex string)

Pass Calldata to OZZOBiT

Include the generated calldata in your NFT checkout configuration:

typescripttypescript

// Build the nftCheckoutData object
const nftCheckoutData = {
  nftContractAddress: '0xYourContractAddress...',
  nftTokenId: '42',
  nftNetwork: 'ethereum',
  nftPrice: ethers.parseEther('0.5'),     // Price in wei
  nftQuantity: 1,
  exchangeCallData: calldata,             // The generated calldata!
}

// Pass to widget URL or SDK
const params = new URLSearchParams({
  apiKey: 'YOUR_KEY',
  productsAvailed: 'NFT',
  nftCheckoutData: JSON.stringify(nftCheckoutData),
})

const widgetUrl = `https://OZZOBiT.com/global?${params.toString()}`

Complete Example

nft-checkout-utils.tstypescript

// utils/nft-calldata.ts
import { ethers } from 'ethers'

interface NFTPurchaseConfig {
  contractAddress: string
  network: string
  tokenId: string | number
  price: string           // In ETH (e.g., "0.5")
  quantity?: number
  buyerAddress: string
}

export async function createNFTCheckoutUrl(config: NFTPurchaseConfig): Promise<string> {
  // 1. Define the ABI for your purchase function
  const abi = ['function buy(uint256 tokenId) payable']
  
  // 2. Create interface and encode
  const iface = new ethers.Interface(abi)
  const calldata = iface.encodeFunctionData('buy', [config.tokenId])
  
  // 3. Convert price to wei
  const priceWei = ethers.parseEther(config.price)
  
  // 4. Build checkout data
  const nftCheckoutData = {
    nftContractAddress: config.contractAddress,
    nftTokenId: String(config.tokenId),
    nftNetwork: config.network,
    nftPrice: priceWei.toString(),
    nftQuantity: config.quantity || 1,
    exchangeCallData: calldata,
  }
  
  // 5. Construct widget URL
  const params = new URLSearchParams({
    apiKey: process.env.OZZOBiT_API_KEY!,
    productsAvailed: 'NFT',
    walletAddress: config.buyerAddress,
    nftCheckoutData: JSON.stringify(nftCheckoutData),
  })
  
  return `https://OZZOBiT.com/global?${params.toString()}`
}

// Usage:
const url = await createNFTCheckoutUrl({
  contractAddress: '0x1234...abcd',
  network: 'ethereum',
  tokenId: 42,
  price: '0.15',
  quantity: 1,
  buyerAddress: '0x742d35Cc6634C0532925a3b844Bc9e7595f8bD21',
})

console.log('NFT Checkout URL:', url)

⚠️

Important Requirements

Your smart contract must be verified on the blockchain explorer
The contract must be whitelisted by OZZOBiT before use
Calldata must exactly match your contract's expected function signature
Test thoroughly on testnets (Goerli/Mumbai) before mainnet use

ℹ️

Need Help?

If you need assistance generating calldata for your specific contract, contact our support team through the Partner Support Hub.