TreeDAO NFTree contract

NFTree.sol

// SPDX-License-Identifier: GPL-3.0

pragma solidity >=0.7.0 <0.9.0;


import "https://raw.githubusercontent.com/OpenZeppelin/openzeppelin-contracts/master/contracts/token/ERC721/presets/ERC721PresetMinterPauserAutoId.sol";


interface TreeToken  {
    function burnFrom(address, uint) external;
    function allowance(address, address) external view returns (uint256);
    function balanceOf(address) external view returns (uint256);
}

contract NFTree is ERC721PresetMinterPauserAutoId("TreeDAO NFTrees", "NFTrees", "https://treedao.org/trees/" ) {
    TreeToken public TreeTokenContract;

    function SetTreeTokenAddress(address tt) public {
        // TODO access control here
        require(hasRole(MINTER_ROLE, msg.sender), "Caller is not a minter");
        TreeTokenContract = TreeToken(tt);
    }

    function GetTreeTokenAddress() public view returns (TreeToken) {
        return TreeTokenContract;
    }

    function ClaimNFTs(uint numberOfNFTrees) public {
        // The dapp must first approve this contract to allow this contract to burn their TreeTokens in exchange for NFTrees
        require(TreeTokenContract.allowance(msg.sender, address(this)) >= numberOfNFTrees * 10**18, "You must approve the NFTree contract to spend your TreeTokens.");
        require(TreeTokenContract.balanceOf(msg.sender) >= numberOfNFTrees * 10**18, "Your balance is too low to claim this many NFTrees");

        // burnFrom msg.sender on the TreeTokenContract
        TreeTokenContract.burnFrom(msg.sender, numberOfNFTrees * 10**18);

        // mint that many NFTs taking care to remember the 18 decimal place difference in resolution
        for (uint i=0; i<numberOfNFTrees; i++) {
            _mint(msg.sender);
        }
    }
}