Enums in Blockchain / Solidity - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Solidity enum code?

Consider this Solidity contract snippet using an enum. What will be the output when getStatus() is called?

Blockchain / Solidity

pragma solidity ^0.8.0;

contract Order {
    enum Status { Pending, Shipped, Delivered, Cancelled }
    Status public status;

    constructor() {
        status = Status.Shipped;
    }

    function getStatus() public view returns (string memory) {
        if (status == Status.Pending) return "Pending";
        else if (status == Status.Shipped) return "Shipped";
        else if (status == Status.Delivered) return "Delivered";
        else return "Cancelled";
    }
}

A "Shipped"

B "Pending"

C "Delivered"

D "Cancelled"

💡 Hint

Look at the constructor and see which enum value is assigned to status.

The constructor sets status to Status.Shipped. The getStatus() function returns the string "Shipped" when the status matches Status.Shipped.

🧠 Conceptual

intermediate

What integer value does the first enum member have in Solidity?

In Solidity, enums start with the first member assigned which integer value?

A Undefined until assigned

B 1

C -1

D 0

💡 Hint

Think about how counting usually starts in programming.

In Solidity, enum members start counting from 0 by default. The first member has the value 0, the second 1, and so on.

🔧 Debug

advanced

Which option causes a runtime error in this Solidity enum usage?

Given this enum and function, which option will cause a runtime error?

enum Color { Red, Green, Blue }

function setColor(uint c) public pure returns (Color) {
    return Color(c);
}

A Calling setColor(1) returns Color.Green

B Calling setColor(0) returns Color.Red

C Calling setColor(3) causes an error

D Calling setColor(2) returns Color.Blue

💡 Hint

Check the valid range of enum values and what happens if you pass a number outside that range.

Enum values in Solidity correspond to integers starting at 0. The enum Color has 3 members (0 to 2). Passing 3 is out of range and causes a runtime error.

📝 Syntax

advanced

Which option correctly declares and uses an enum in Solidity?

Choose the correct Solidity code snippet that declares an enum and assigns a value to a state variable.

A

enum State { Active, Inactive }
State public state = State.Active;

B

enum State { Active, Inactive }
State public state = Active;

C

enum State { Active, Inactive }
State state = State[0];

D

enum State { Active, Inactive }
State state = 1;

💡 Hint

Remember how to refer to enum members with their enum type.

Option A correctly declares the enum and assigns the member using State.Active. Option A misses the enum type prefix. Option A uses invalid syntax with brackets. Option A assigns an integer directly without casting to the enum type, which is invalid in Solidity.

🚀 Application

expert

How many items are in the enum after this Solidity code runs?

Given this enum and contract, how many enum members exist?

pragma solidity ^0.8.0;

contract TrafficLight {
    enum Light { Red, Yellow, Green }

    function countLights() public pure returns (uint) {
        return uint(type(Light).max) + 1;
    }
}

A 2

B 3

C 4

D Compilation error

💡 Hint

Look at how type(Light).max relates to enum members.

The enum Light has three members: Red (0), Yellow (1), Green (2). The maximum value is 2, so adding 1 gives the total count 3.