Function modifiers in Blockchain / Solidity - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a function modifier named onlyOwner.

Blockchain / Solidity

modifier [1]() {
    _;
}

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

AcheckOwner

BownerOnly

ConlyOwner

DownerModifier

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different modifier name than declared.

Forgetting the modifier keyword.

The modifier name is onlyOwner as declared in the code.

2fill in blank

medium

Complete the code to require that the caller is the owner inside the onlyOwner modifier.

Blockchain / Solidity

modifier onlyOwner() {
    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 != which would reject the owner.

Using comparison operators like < or > which are invalid for addresses.

The require statement checks if msg.sender is equal to owner.

3fill in blank

hard

Fix the error in the modifier usage in the function declaration.

Blockchain / Solidity

function withdraw() public [1] {
    // withdraw logic
}

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

AonlyOwner

BonlyOwner()

ConlyOwner{}

DonlyOwner;

Attempts:

3 left

💡 Hint

Common Mistakes

Adding parentheses after the modifier name when it has no parameters.

Using braces or semicolons after the modifier name.

Modifiers are used without parentheses if they have no parameters.

4fill in blank

hard

Fill both blanks to create a modifier that checks if the caller is the owner and then executes the function.

Blockchain / Solidity

modifier [1]() {
    require(msg.sender [2] owner, "Caller is not owner");
    _;
}

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

AonlyOwner

B==

C!=

DownerOnly

Attempts:

3 left

💡 Hint

Common Mistakes

Using != which rejects the owner.

Using a wrong modifier name.

The modifier name is onlyOwner and the require condition uses == to check ownership.

5fill in blank

hard

Fill all three blanks to create a modifier named onlyOwner that requires the caller to be the owner and then executes the function.

Blockchain / Solidity

modifier [1]() {
    require(msg.sender [2] owner, "Not owner");
    [3];
}

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

AownerOnly

B==

C_

DonlyOwner

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong modifier names.

Forgetting the _; statement.

The modifier is named onlyOwner, uses == to check ownership, and _; to continue execution.