Transfer ERC721 tokens in BULK to single address

Question

I want to know what is the gas effective manner to code to transfer many (e.g 1000) ERC721 tokens to a single address. I have tried the way below but I want something more efficient.

    function bulkTransfer(uint256[] tokenIds, address _to) public onlyOwner {
        uint256 length = tokenIds.length;
        for (uint256 i = 0; i < length; i++) {
            _transfer(owner, _to, tokenIds[i]);
        }
    }

Assume that the owner holds all these tokens in that array.

Answer 1

You can add these gas saving methods:

function bulkTransfer(uint256[] tokenIds, address _to) external onlyOwner {
        for (uint256 i; i < tokenIds.length;) {
            _transfer(msg.sender, _to, tokenIds[I]);
            unchecked { i++ }
        }
}

Here is what did I do:

• change the visibility to external
• delete the length variable. Because reading from calldata is not that expensive.
• change i=0 to i. Because the default value for uint is already 0.
• delete i++ and add unchecked { i++ }. This means, "solidity, believe me, there will be no over/underflows".
• change owner to msg.sender. Because we don't want to read every time from the storage. Since the function is onlyOwner, msg.sender should be the owner.

Answer 2

I made a small (free) tool that helps when transferring multiple NFTs from an ERC721: https://theforever.io/erc721-batch-transfer-tool

This assumes that you've already transferred the tokens to your own wallet. Using the tool, you can enter a list of addresses and token_ids to batch transfer the ERC721 NFTs to whoever you like. It's more gas-efficient than doing it in multiple transactions.

Answer 3

IF THE CONTRACT IS ALREADY DEPLOYED, I have implemented already and published it here https://nft.life.

You can see quite a few people have used it. It's free and open source.