Minimal proxy (clone) pattern in Blockchain / Solidity - Mini Project: Build & Apply

Minimal Proxy (Clone) Pattern in Solidity

📖 Scenario: You are building a smart contract system on Ethereum. You want to create many lightweight copies (clones) of a main contract to save gas and storage. This is useful when you have a standard contract logic but want separate instances for different users.

🎯 Goal: Build a minimal proxy contract that clones a main contract using the EIP-1167 minimal proxy pattern. You will create the main contract, then write a factory contract that deploys clones pointing to the main contract.

📋 What You'll Learn

Create a main contract called LogicContract with a public uint variable value and a function setValue(uint _value) to update it.

Create a factory contract called CloneFactory with a function createClone(address target) that deploys a minimal proxy clone of target using assembly.

Store the address of the deployed clone in a public variable lastClone.

Write a function getCloneValue() in the factory that calls value() on the last clone and returns it.

Print the address of the last clone and the value stored in it.

💡 Why This Matters

🌍 Real World

Minimal proxy clones save gas and storage on Ethereum by reusing contract logic. This pattern is widely used in DeFi and NFT projects to deploy many instances cheaply.

💼 Career

Understanding minimal proxies is important for blockchain developers working on scalable smart contract systems and optimizing gas costs.

1

Create the main contract with a value variable and setter

Create a contract called LogicContract with a public uint variable named value. Add a public function setValue(uint _value) that sets value to _value.

Blockchain / Solidity

// Your code here

Need a hint?

Think of LogicContract as the main blueprint. It has a number value and a way to change it.

2

Add the clone factory contract with createClone function

Create a contract called CloneFactory. Inside it, declare a public address variable lastClone. Add a public function createClone(address target) that deploys a minimal proxy clone of target using assembly and stores the clone address in lastClone. Use the standard EIP-1167 bytecode pattern for the clone.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract LogicContract {
    uint public value;

    function setValue(uint _value) public {
        value = _value;
    }
}

contract CloneFactory {
    address public lastClone;

    // Your code here
}

Need a hint?

Use assembly to write the minimal proxy bytecode. The pattern is fixed and uses the create opcode.

3

Add a function to get the value from the last clone

In the CloneFactory contract, add a public view function getCloneValue() that calls the value() function on the lastClone address using staticcall and returns the uint value.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract LogicContract {
    uint public value;

    function setValue(uint _value) public {
        value = _value;
    }
}

contract CloneFactory {
    address public lastClone;

    function createClone(address target) public returns (address result) {
        bytes20 targetBytes = bytes20(target);
        assembly {
            let clone := mload(0x40)
            mstore(clone, 0x3d602d80600a3d3981f3)
            mstore(add(clone, 0x14), shl(0x60, targetBytes))
            mstore(add(clone, 0x28), 0x5af43d82803e903d91602b57fd5bf3)
            result := create(0, clone, 0x37)
        }
        lastClone = result;
    }

    function getCloneValue() public view returns (uint val) {
        // Your code here
    }
}

Need a hint?

Use staticcall to safely call the value() function on the clone without changing state.

4

Print the last clone address and its stored value

Add a public view function printLastCloneInfo() in CloneFactory that returns the lastClone address and the uint value from getCloneValue(). Then write a simple script or test that deploys LogicContract, deploys CloneFactory, creates a clone of LogicContract, sets the value on the clone to 42, and prints the clone address and value.

Blockchain / Solidity

pragma solidity ^0.8.0;

contract LogicContract {
    uint public value;

    function setValue(uint _value) public {
        value = _value;
    }
}

contract CloneFactory {
    address public lastClone;

    function createClone(address target) public returns (address result) {
        bytes20 targetBytes = bytes20(target);
        assembly {
            let clone := mload(0x40)
            mstore(clone, 0x3d602d80600a3d3981f3)
            mstore(add(clone, 0x14), shl(0x60, targetBytes))
            mstore(add(clone, 0x28), 0x5af43d82803e903d91602b57fd5bf3)
            result := create(0, clone, 0x37)
        }
        lastClone = result;
    }

    function getCloneValue() public view returns (uint val) {
        (bool success, bytes memory data) = lastClone.staticcall(abi.encodeWithSignature("value()"));
        require(success, "Call failed");
        val = abi.decode(data, (uint));
    }

    function printLastCloneInfo() public view returns (address cloneAddress, uint cloneValue) {
        // Your code here
    }
}

// Script or test code to deploy and interact
// Your code here

Need a hint?

Return both the clone address and its stored value. The test script simulates deployment and interaction.