Timelock pattern in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a public variable named 'delay' of type uint.

Blockchain / Solidity

uint public [1];

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Alock

Btime

Cdelay

Dduration

Attempts:

3 left

💡 Hint

Common Mistakes

Using a variable name that does not describe the delay.

Forgetting to make the variable public.

The variable delay holds the time delay for the timelock. It must be declared as public and of type uint.

2fill in blank

medium

Complete the function signature to set a new admin address.

Blockchain / Solidity

function [1](address newAdmin) external onlyAdmin { admin = newAdmin; }

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AupdateAdmin

BsetAdmin

CchangeAdmin

DmodifyAdmin

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name that is too vague or uncommon.

Not using a verb that clearly indicates setting a value.

The function to set a new admin is commonly named setAdmin to clearly indicate its purpose.

3fill in blank

hard

Fix the error in the require statement to check if the current time is past the unlock time.

Blockchain / Solidity

require(block.timestamp [1] unlockTime, "Timelock not expired");

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A==

B<

C<=

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>=' causing premature execution.

Using '==' which is too strict and may block valid calls.

The require statement should check if the current time is greater than or equal to the unlock time to allow execution after the delay.

4fill in blank

hard

Fill both blanks to create a mapping that stores queued transactions and a function to queue a transaction.

Blockchain / Solidity

mapping(bytes32 => bool) public [1];

function [2](bytes32 txHash) public onlyAdmin { queuedTransactions[txHash] = true; }

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AqueuedTransactions

BpendingTx

CqueueTransaction

DaddTransaction

Attempts:

3 left

💡 Hint

Common Mistakes

Using inconsistent names between mapping and function.

Choosing vague names that do not describe their purpose.

The mapping is named queuedTransactions to store transaction hashes. The function to add a transaction is queueTransaction.

5fill in blank

hard

Fill all three blanks to implement the executeTransaction function with checks for queued status, timelock, and deletion after execution.

Blockchain / Solidity

function [1](bytes32 txHash) public onlyAdmin {
    require(queuedTransactions[txHash], "Transaction not queued");
    require(block.timestamp [2] unlockTime, "Timelock not expired");
    queuedTransactions[txHash] = [3];
    // execute transaction logic here
}

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AexecuteTransaction

B>=

Cfalse

Dtrue

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect comparison operators in the require statement.

Not marking the transaction as executed (false) after running.

The function is named executeTransaction. It checks if the current time is greater than or equal to the unlock time, then sets the queued transaction to false after execution.