Indexed parameters in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare an indexed parameter in an event.

Blockchain / Solidity

event Transfer(address [1] from, address to, uint256 value);

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

Aindexed

Bpublic

Cmemory

Dpayable

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'public' or 'memory' instead of 'indexed' for event parameters.

Forgetting to add 'indexed' before the parameter name.

The keyword indexed marks a parameter as indexed, allowing it to be searched in event logs.

2fill in blank

medium

Complete the event declaration to index the 'to' address parameter.

Blockchain / Solidity

event Transfer(address from, address [1] to, uint256 value);

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

Apublic

Bpayable

Cmemory

Dindexed

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'memory' or 'payable' instead of 'indexed'.

Placing 'indexed' after the parameter name.

Marking the 'to' parameter as indexed allows filtering events by recipient address.

3fill in blank

hard

Fix the error in the event declaration by correctly indexing the 'owner' parameter.

Blockchain / Solidity

event Approval(address [1] owner, address spender, uint256 value);

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

Apublic

Bindexed

Cmemory

Dpayable

Attempts:

3 left

💡 Hint

Common Mistakes

Placing 'indexed' after the parameter name.

Using incorrect keywords like 'payable' or 'memory'.

The 'owner' parameter must be marked with indexed before its name to be searchable in logs.

4fill in blank

hard

Fill both blanks to declare an event with two indexed address parameters.

Blockchain / Solidity

event Transfer(address [1] from, address [2] to, uint256 value);

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

Aindexed

Bpayable

Cmemory

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Indexing only one parameter when two are needed.

Using wrong keywords like 'payable' or 'memory'.

Both 'from' and 'to' parameters are marked indexed to allow filtering by sender and recipient.

5fill in blank

hard

Fill all three blanks to declare an event with three indexed parameters: two addresses and one uint.

Blockchain / Solidity

event Approval(address [1] owner, address [2] spender, uint256 [3] value);

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

Aindexed

Bpayable

Cmemory

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Indexing fewer than three parameters.

Using incorrect keywords like 'payable' or 'memory'.

All three parameters are marked indexed to allow filtering by owner, spender, and value.