Mastering Blockchain Programming with Solidity

The _transferFrom internal function

_transferFrom() is an internal function, which is used to transfer the given token from the current owner's account to the receiver's account.

The function takes three arguments:

• from: The address of the owner who currently owns the given token
• to: The address of the receiver or the new owner that will receive the transferred token
• tokenId: The NFT ID of the token that is to be transferred from the from address to the to address

Let's look at the _transferFrom() function code:

function _transferFrom(address from, address to, uint256 tokenId) internal {    require(ownerOf(tokenId) == from);    require(to != address(0));    _clearApproval(tokenId);    _ownedTokensCount[from] = _ownedTokensCount[from].sub(1);    _ownedTokensCount[to] ...