Return values in Blockchain / Solidity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Solidity function call?

Consider the following Solidity function that returns a value. What will be the output when getValue() is called?

Blockchain / Solidity

pragma solidity ^0.8.0;

contract Test {
    function getValue() public pure returns (uint) {
        uint a = 5;
        uint b = 10;
        return a + b;
    }
}

A 10

B 5

C 15

D Compilation error

💡 Hint

Look at the return statement carefully. It adds two numbers.

The function adds a and b which are 5 and 10 respectively, so it returns 15.

❓ Predict Output

intermediate

What does this smart contract function return?

Given the following Solidity function, what is the output when getGreeting() is called?

Blockchain / Solidity

pragma solidity ^0.8.0;

contract Greeter {
    function getGreeting() public pure returns (string memory) {
        return "Hello, Blockchain!";
    }
}

A "Hello, Blockchain!"

B "Hello, World!"

C Compilation error due to missing memory keyword

D Empty string

💡 Hint

Check the string returned exactly as written.

The function returns the string literal "Hello, Blockchain!" exactly as coded.

❓ Predict Output

advanced

What is the output of this Solidity function with multiple returns?

What will be the output of calling getData() in the following contract?

Blockchain / Solidity

pragma solidity ^0.8.0;

contract Data {
    function getData() public pure returns (uint, bool) {
        uint x = 42;
        bool y = true;
        return (x, y);
    }
}

A Compilation error due to missing tuple return

B (42, true)

C 42

D (true, 42)

💡 Hint

Look at the order of the returned values in the function signature.

The function returns a tuple with uint first and bool second, so the output is (42, true).

❓ Predict Output

advanced

What error does this Solidity function produce?

What error will occur when calling brokenFunction() in this contract?

Blockchain / Solidity

pragma solidity ^0.8.0;

contract Broken {
    function brokenFunction() public pure returns (uint) {
        uint a = 10;
        // Missing return statement
    }
}

A No error, returns 10

B Runtime error: Division by zero

C Returns 0 by default

D Compilation error: Missing return statement

💡 Hint

Functions with a return type must have a return statement.

The function declares it returns a uint but does not have a return statement, causing a compilation error.

🧠 Conceptual

expert

Which option correctly describes the behavior of return values in Solidity functions?

Choose the statement that best describes how return values work in Solidity functions.

A Functions must always explicitly return a value if a return type is declared; otherwise, a compilation error occurs.

B Functions can omit return statements even if a return type is declared; the default zero value is returned automatically.

C Functions can return multiple values only if they are declared as external functions.

D Functions without a return type can still return values without errors.

💡 Hint

Think about Solidity's strict typing and return requirements.

In Solidity, if a function declares a return type, it must explicitly return a value of that type; otherwise, the compiler throws an error.