Listing All Tokens of a User
Step 1: Import ERC-20 Interfaces
First, we need to import the ERC-20 interface into our contract to access the required functions. Create an interface like this:
Solidity
interface IERC20 { function balanceOf(address _owner) external view returns (uint256); } |
This step ensures our contract can interact with ERC-20 tokens.
Step 2: Create a Function to List Tokens
Next, we’ll implement a function that lists all tokens of a user. This function will loop through known ERC-20 token addresses and call the balanceOf function for each token contract, passing the user’s address as an argument.
Solidity
function listUserTokens(address _user, address[] memory _tokenAddresses) public view returns (uint256[] memory) { uint256[] memory userTokenBalances = new uint256[](_tokenAddresses.length); for (uint256 i = 0; i < _tokenAddresses.length; i++) { IERC20 token = IERC20(_tokenAddresses[i]); userTokenBalances[i] = token.balanceOf(_user); } return userTokenBalances; } |
We define a function called listUserTokens, which takes the user’s address and an array of token addresses as input. It then loops through the token addresses, calls balanceOf for each token contract, and stores the balances in an array.
Step 3: Deploy Your Contract and Call the Function
Deploy your contract on the Ethereum blockchain, and when calling the listUserTokens function, pass an array of ERC-20 token addresses. This will return an array of token balances for the specified user.
Solidity
pragma solidity ^0.8.0; // Import the ERC-20 interface interface IERC20 { function balanceOf(address _owner) external view returns (uint256); } contract TokenLister { // Function to list user tokens function listUserTokens(address _user, address[] memory _tokenAddresses) public view returns (uint256[] memory) { uint256[] memory userTokenBalances = new uint256[](_tokenAddresses.length); for (uint256 i = 0; i < _tokenAddresses.length; i++) { IERC20 token = IERC20(_tokenAddresses[i]); userTokenBalances[i] = token.balanceOf(_user); } return userTokenBalances; } } |
Output:
How to List all Tokens of User in Solidity
Ethereum, the main blockchain stage for decentralized applications (DApps), permits designers to make many advanced resources, including tokens. This article focuses on discussing the technique to list all the tokens of a user in Solidity.