DeclarationError: Undeclared identifier error when using _setBaseURI

[martriay]

Hello Matteo, welcome to the forum! What version of Contracts are you using?

ERC721 comes with _setTokenUri now. Check this previous discussion:

Why doesn't OpenZeppelin ERC721 contain setTokenURI?

Hi @novaknole! This was split off into a separate contract called ERC721URIStorage, because using storage in this way is expensive and we decided to make the default mechanism significantly cheaper. You may find these threads useful: Function _setTokenURI() in ERC721 is gone with pragma ^0.8.0 OpenZeppelin Contracts 4.0 Beta