Access control with OpenZeppelin in Blockchain / Solidity - Mini Project: Build & Apply

Access control with OpenZeppelin

📖 Scenario: You are creating a simple smart contract for a club membership system on the Ethereum blockchain. Only the club owner should be able to add new members. To manage this, you will use OpenZeppelin's Access Control features.

🎯 Goal: Build a smart contract that uses OpenZeppelin's Ownable contract to restrict the ability to add members only to the owner of the contract.

📋 What You'll Learn

Use OpenZeppelin's Ownable contract for access control

Create a mapping to store members' addresses and their membership status

Write a function addMember that only the owner can call to add a member

Write a function isMember to check if an address is a member

💡 Why This Matters

🌍 Real World

Access control is essential in blockchain contracts to restrict sensitive actions to authorized users, such as owners or admins.

💼 Career

Understanding OpenZeppelin's access control contracts is a key skill for blockchain developers working on secure smart contracts.

1

Set up the contract and member storage

Create a Solidity contract named Club. Import OpenZeppelin's Ownable contract. Inside Club, create a public mapping called members that maps address to bool to store membership status.

Blockchain / Solidity

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";

contract Club is Ownable {
    // Your code here
}

Need a hint?

Use mapping(address => bool) public members; inside the contract to store membership.

2

Add a function to add members with owner restriction

Add a public function named addMember that takes an address parameter called newMember. Use the onlyOwner modifier to restrict access. Inside the function, set members[newMember] to true.

Blockchain / Solidity

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";

contract Club is Ownable {
    mapping(address => bool) public members;

    // Your code here
}

Need a hint?

Use the onlyOwner modifier to restrict the addMember function.

3

Add a function to check membership status

Add a public view function named isMember that takes an address parameter called user and returns a bool. The function should return the membership status from the members mapping.

Blockchain / Solidity

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";

contract Club is Ownable {
    mapping(address => bool) public members;

    function addMember(address newMember) public onlyOwner {
        members[newMember] = true;
    }

    // Your code here
}

Need a hint?

Return the membership status from the members mapping inside isMember.

4

Test the membership addition and check

Add a public function named testMembership that calls addMember with your own address msg.sender and then returns the result of isMember(msg.sender). Print the result using return.

Blockchain / Solidity

pragma solidity ^0.8.0;

import "@openzeppelin/contracts/access/Ownable.sol";

contract Club is Ownable {
    mapping(address => bool) public members;

    function addMember(address newMember) public onlyOwner {
        members[newMember] = true;
    }

    function isMember(address user) public view returns (bool) {
        return members[user];
    }

    // Your code here
}

Need a hint?

Call addMember(msg.sender) and then return isMember(msg.sender) inside testMembership.