Require, assert, and revert in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to check if the sender is the owner using require.

Blockchain / Solidity

require(msg.sender [1] owner, "Not owner");

Drag options to blanks, or click blank then click option'

A==

B!=

C<

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' instead of '==' causes the check to fail when sender is owner.

Using '<' or '>' operators for address comparison is invalid.

The require statement checks if msg.sender is equal to owner. If not, it stops execution with the message "Not owner".

2fill in blank

medium

Complete the code to revert the transaction with a message if the balance is insufficient.

Blockchain / Solidity

if (balance < amount) [1]("Insufficient balance");

Drag options to blanks, or click blank then click option'

Arequire

Bthrow

Crevert

Dassert

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'throw' is deprecated in Solidity.

Using 'assert' is for internal errors, not user input checks.

The revert statement stops execution and reverts all changes with the given message.

3fill in blank

hard

Fix the error in the assert statement to check that totalSupply is not zero.

Blockchain / Solidity

assert([1] != 0);

Drag options to blanks, or click blank then click option'

Abalance

BtotalSupply

Cmsg.sender

Downer

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'msg.sender' or 'owner' in assert for this check is incorrect.

Checking 'balance' instead of 'totalSupply' does not verify total tokens.

The assert checks that totalSupply is not zero, ensuring the contract state is valid.

4fill in blank

hard

Fill both blanks to create a require statement that checks if amount is greater than zero.

Blockchain / Solidity

require(amount [1] 0, "Amount must be positive");
assert(amount [2] 0);

Drag options to blanks, or click blank then click option'

A>

B<

C==

D!=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' or '==' will not correctly check for positive amounts.

Using '!=' does not ensure amount is positive.

Both require and assert check that amount is greater than zero to ensure valid input.

5fill in blank

hard

Fill all three blanks to create a revert statement inside an if block that checks if sender is not owner.

Blockchain / Solidity

if (msg.sender [1] owner) {
    [2]("Unauthorized");
    [3];
}

Drag options to blanks, or click blank then click option'

A!=

Brevert

Creturn

Drequire

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'require' inside the if block is redundant here.

Not returning after revert can cause unexpected behavior.

The code checks if msg.sender is not the owner. If true, it reverts with "Unauthorized" and returns to stop execution.