Upgrade strategies in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a new version number for a smart contract upgrade.

Blockchain / Solidity

uint256 public constant VERSION = [1];

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Av1

B"1"

Cversion1

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for the version.

Using an undefined variable name.

The version number should be a numeric constant, so 1 is correct.

2fill in blank

medium

Complete the code to emit an event when the contract is upgraded.

Blockchain / Solidity

event Upgraded(address indexed [1]);

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Asender

Bowner

Cupgrader

Dcaller

Attempts:

3 left

💡 Hint

Common Mistakes

Using generic names like owner which may not reflect the upgrader.

Using sender which is less descriptive here.

The event should log the address of the upgrader, so upgrader is the best choice.

3fill in blank

hard

Fix the error in the upgrade function to correctly call the new implementation.

Blockchain / Solidity

function upgradeTo(address newImplementation) external [1] {
    require(newImplementation != address(0), "Invalid address");
    _implementation = newImplementation;
    emit Upgraded(msg.sender);
}

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Apublic

BonlyOwner

Cexternal onlyOwner

Dprivate

Attempts:

3 left

💡 Hint

Common Mistakes

Leaving the function public without access control.

Using private which prevents external calls.

The upgrade function should be restricted to the contract owner, so the onlyOwner modifier is needed.

4fill in blank

hard

Fill both blanks to create a mapping that stores upgrade timestamps and a function to check if upgrade is allowed.

Blockchain / Solidity

mapping(address => uint256) public [1];

function canUpgrade(address upgrader) public view returns (bool) {
    return block.timestamp >= [2][upgrader] + 1 days;
}

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AlastUpgradeTime

BupgradeTimes

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the mapping and in the function.

Choosing unclear or inconsistent variable names.

The mapping and the function should use the same name lastUpgradeTime to track timestamps.

5fill in blank

hard

Fill all three blanks to implement a function that upgrades the contract only if the new version is higher and updates the version number.

Blockchain / Solidity

function upgradeToVersion(uint256 newVersion, address newImplementation) external [1] {
    require(newVersion > [2], "Version must be higher");
    upgradeTo(newImplementation);
    [3] = newVersion;
}

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AonlyOwner

BVERSION

CcurrentVersion

D_version

Attempts:

3 left

💡 Hint

Common Mistakes

Not restricting the function to the owner.

Comparing with the wrong version variable.

Not updating the version after upgrade.

The function should be restricted to the owner (onlyOwner), compare with currentVersion, and update _version.