Guarantee a contract can only receive one type of ERC721 nft

Creating a contract for a privateSale fo ERC721 NFTs, first I mint some inventory to the privateSale contract address implementing onErc721Received(...) what I want to guarantee is that this privateSaleContract does only receive ERC721 tokens from one given NFT type (by its contract address)

How can I guarantee that?

Solution 1:

The ERC721 standard defines two types of transfer functions:

• safeTransferFrom() that checks if the receiver is a contract - and if it is, tries to execute the onERC721Received() function on the receiver.
• But also a non-safe transfer function (transferFrom()) that is not supposed to call the onERC721Received().

So anyone can send you NFTs using the non-safe transfer function without invoking any function on your contract. Which makes these transfers unblockable.