Mastering Blockchain Programming with Solidity

The balanceOf function

As we have seen in Chapter 7, ERC20 Token Standard, the ERC20 implementation also has a balanceOf() function to check the token balance of a particular account. Here, in the case of the ERC721 implementation, the function returns the number of NFT tokens that the provided address owns:

function balanceOf(address owner) public view returns (uint256) {    require(owner != address(0));    return _ownedTokensCount[owner];}

As you can see in the preceding code that if the owner address provided in the function argument is address(0), the function call will fail. Here, address(0) is also represented as address(0x0) or 0x0000000000000000000000000000000000000000. As in the ERC721 implementation, it is not possible to send tokens ...