SafeTransferFrom

SafeTransferFrom is a function defined in the ERC-721 standard for non-fungible tokens. It transfers the ownership of a token identified by tokenId from one address to another, with an added safety mechanism that prevents tokens from being sent to contracts that cannot handle them.

There are two overloads: safeTransferFrom(address from, address to, uint256 tokenId) and safeTransferFrom(address from, address to, uint256 tokenId, bytes data). The data parameter is forwarded to the recipient’s onERC721Received function when applicable. The safety feature requires that if the recipient is a smart contract, it must implement the IERC721Receiver interface and return the expected selector from onERC721Received; otherwise the transfer reverts.

Requirements and behavior: The caller must be the token owner or be approved to transfer the token. The token must be owned by the specified from address, and the to address must not be the zero address. Upon success, the token is transferred and a Transfer event is emitted. The internal workflow involves performing the transfer and then invoking a check on the recipient with _checkOnERC721Received to ensure the recipient can handle ERC-721 tokens.

Relation to transferFrom: safeTransferFrom adds a safety layer that transferFrom lacks. While transferFrom transfers a token without verifying the recipient’s ability to receive it, safeTransferFrom protects against tokens being locked in contracts that do not implement the required interface.

In practice, safeTransferFrom is the recommended method for transferring NFTs to addresses that may include smart contracts, ensuring compatibility and reducing the risk of token loss.