ownerOfuint256

ownerOf(uint256) is a standard function in the ERC-721 Non-Fungible Token (NFT) specification. It returns the address of the current owner of the specified token identified by tokenId. The canonical signature is function ownerOf(uint256 tokenId) external view returns (address owner).

In typical implementations, ownership is tracked with internal storage (for example, a mapping from tokenId to owner). The function is a read-only call and does not modify contract state. It reverts if the token does not exist, or if the token’s owner is not defined, to prevent returning an invalid address. This behavior aligns with the ERC-721 requirement that tokens either exist with a valid owner or do not exist at all.

The ownerOf function is central to token governance. It is used by wallets, marketplaces, and other smart contracts to verify who currently owns a token, and it underpins access control for transfers and approvals. An owner may authorize another address to transfer the token on its behalf by using approve or setApprovalForAll, while ownerOf itself solely reports ownership.

Existence and transfers: when a token is minted, the owner is set and ownerOf(tokenId) returns that address. When a token is burned or never minted, ownerOf will typically revert. Transfers emit a Transfer event, and ownership changes are reflected in subsequent ownerOf queries.

Usage notes: in Solidity, a typical implementation returns the owner address after a nonzero check. In web3 or ethers.js, callers use contract.methods.ownerOf(tokenId).call() to fetch the owner off-chain.