Ethereum Cookbook

How to do it…

1. To check the balance of tokens in each address, the usual balanceOf function from ERC-20 is present in the standard. It accepts an address as input and returns the number of non-fungible tokens owned by the address. Create the same function to store the balances:

function balanceOf(address _owner) external view returns (uint256);

2. Create a mapping with the address as the key and count as the value to store the number of tokens:

mapping (address => uint256) internal ownedTokensCount;

3. Modify the balanceOf function to read the value from the mapping:

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

4. Since the ownership of each token can be ...