I am trying to lazy mint NFTs with a voucher. I am mostly using the codes from this GitHub repo: https://github.com/ipfs-shipyard/nft-school-examples/tree/main/lazy-minting . I have decided to add two new parameters (a uint256 parameter royaltyAmount and an address royaltyReceiver) inside the NFTVoucher (in LazyMinter class). I also described new parameters inside the smart contract's _hash function. After adding this I started receiving the wrong address (a completely arbitrary address) from the smart contract's _verify function. Can someone help me?

Below is how I added new parameters to the createVoucher function:

   * Creates a new NFTVoucher object and signs it using this LazyMinter's signing key.
   * @param {ethers.BigNumber | number} tokenId the id of the un-minted NFT
   * @param {string} uri the metadata URI to associate with this NFT
   * @param {ethers.utils.getAddress | address} royaltyReceiver the address of which the royalty fee will be sent
   * @param {ethers.BigNumber | number} royaltyAmount the percentage of royalty fee
   * @param {ethers.BigNumber | number} minPrice the minimum price (in wei) that the creator will accept to redeem this NFT. defaults to zero
   * @returns {NFTVoucher}
  async createVoucher(tokenId, uri, royaltyReceiver, royaltyAmount, minPrice = 0) {
    const voucher = { tokenId, minPrice, uri, royaltyReceiver, royaltyAmount}
    const domain = await this._signingDomain()
    const types = {
      NFTVoucher: [
        {name: "tokenId", type: "uint256"},
        {name: "minPrice", type: "uint256"},
        {name: "uri", type: "string"},
        {name: "royaltyReceiver", type: "address"},
        {name: "royaltyAmount", type: "uint256"}

and in my smart contract, I changed the _hash like this:

// @notice Returns a hash of the given NFTVoucher, prepared using EIP712 typed data hashing rules.
  /// @param voucher An NFTVoucher to hash.
  function _hash(NFTVoucher calldata voucher) internal view returns (bytes32) {
    return _hashTypedDataV4(keccak256(abi.encode(
      keccak256("NFTVoucher(uint256 tokenId,uint256 minPrice,string uri, address royaltyReceiver, uint256 royaltyAmount)"),

I also changed the NFTVoucher struct like this:

/// @notice Represents an un-minted NFT, which has not yet been recorded into the blockchain. A signed voucher can be redeemed for a real NFT using the redeem function.
  struct NFTVoucher {
    /// @notice The id of the token to be redeemed. Must be unique - if another token with this ID already exists, the redeem function will revert.
    uint256 tokenId;

    /// @notice The minimum price (in wei) that the NFT creator is willing to accept for the initial sale of this NFT.
    uint256 minPrice;

    /// @notice The metadata URI to associate with this token.
    string uri;

    /// @notice The address of which the royalty fee will be sent.
    address royaltyReceiver;

    /// @notice The percentage of royalty fee
    uint256 royaltyAmount;

    /// @notice the EIP-712 signature of all other fields in the NFTVoucher struct. For a voucher to be valid, it must be signed by an account with the MINTER_ROLE.
    bytes signature;

1 Answer 1


So the problem was my createVoucher was returning the NFTVoucher in a different order than how I defined the NFTVoucher struct in my smart contract.

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