State variables in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a state variable named count of type uint.

Blockchain / Solidity

contract Counter {
    [1] count;
}

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Afunction

Buint

Cevent

Dmapping

Attempts:

3 left

💡 Hint

Common Mistakes

Using function instead of a data type.

Trying to declare state variables without a type.

The keyword uint declares an unsigned integer state variable named count.

2fill in blank

medium

Complete the code to initialize the state variable owner with the address of the contract creator.

Blockchain / Solidity

contract Ownership {
    address public owner = [1];
}

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Athis

Bowner

Cmsg.sender

Daddress(0)

Attempts:

3 left

💡 Hint

Common Mistakes

Using this which refers to the contract itself, not the creator.

Using address(0) which is the zero address.

msg.sender is the address that called the contract, usually the creator during deployment.

3fill in blank

hard

Fix the error in the code by completing the declaration of the state variable balance as a private unsigned integer.

Blockchain / Solidity

contract Wallet {
    [1] uint balance;
}

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Apublic

Bexternal

Cinternal

Dprivate

Attempts:

3 left

💡 Hint

Common Mistakes

Using external which is invalid for state variables.

Using public when privacy is needed.

The keyword private restricts access to the balance variable to inside the contract only.

4fill in blank

hard

Fill both blanks to declare a state variable data as a public string and initialize it with "Hello".

Blockchain / Solidity

contract Example {
    [1] public data = [2];
}

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Astring

B"Hello"

C"World"

Dbytes

Attempts:

3 left

💡 Hint

Common Mistakes

Using bytes instead of string for text.

Forgetting quotes around the text.

string declares the variable type, and "Hello" initializes it with the text.

5fill in blank

hard

Fill all three blanks to declare a private unsigned integer totalSupply, initialize it to 1000, and make it accessible via a public function getSupply.

Blockchain / Solidity

contract Token {
    [1] uint totalSupply = [2];
    function getSupply() public view returns (uint) {
        return [3];
    }
}

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

Aprivate

B1000

CtotalSupply

Dpublic

Attempts:

3 left

💡 Hint

Common Mistakes

Using public instead of private for the variable.

Returning a wrong variable or literal in the function.

private hides the variable, 1000 sets its initial value, and totalSupply returns it in the function.