Why functions define contract behavior in Blockchain / Solidity - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a function named setOwner.

Blockchain / Solidity

function [1](address newOwner) public {
    owner = newOwner;
}

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

AsetOwner

BgetOwner

CownerSet

DchangeOwner

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name that does not match the action, like 'getOwner' which suggests reading, not setting.

The function name setOwner clearly defines the behavior to set a new owner in the contract.

2fill in blank

medium

Complete the code to declare a function that returns the owner address.

Blockchain / Solidity

function [1]() public view returns (address) {
    return owner;
}

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

AownerAddress

BsetOwner

Cowner

DgetOwner

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function name that implies changing state, like 'setOwner', when the function only returns data.

The function getOwner clearly indicates it returns the current owner address without changing state.

3fill in blank

hard

Fix the error in the function declaration to make it a valid Solidity function.

Blockchain / Solidity

function setOwner(address newOwner) [1] {
    owner = newOwner;
}

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Apublic

Breturns (address)

Cprivate

Dview

Attempts:

3 left

💡 Hint

Common Mistakes

Using view or returns incorrectly in a function that modifies state.

The function must be declared public to be callable from outside the contract.

4fill in blank

hard

Fill both blanks to complete a function that checks if the caller is the owner before changing it.

Blockchain / Solidity

function [1](address newOwner) public {
    require(msg.sender [2] owner, "Not owner");
    owner = newOwner;
}

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AsetOwner

B==

C!=

DtransferOwner

Attempts:

3 left

💡 Hint

Common Mistakes

Using '!=' instead of '==' in the require condition, which would reject the owner.

The function setOwner changes the owner only if the caller is the current owner, checked by msg.sender == owner.

5fill in blank

hard

Fill all three blanks to create a function that emits an event when the owner changes.

Blockchain / Solidity

event OwnerChanged(address indexed oldOwner, address indexed newOwner);

function [1](address newOwner) public {
    require(msg.sender == owner, "Not owner");
    address [2] = owner;
    owner = newOwner;
    emit [3](oldOwner, newOwner);
}

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

AchangeOwner

BoldOwner

COwnerChanged

DsetOwner

Attempts:

3 left

💡 Hint

Common Mistakes

Not storing the old owner before changing it, causing incorrect event data.

The function setOwner updates the owner and emits the OwnerChanged event with the old and new owner addresses.