Enums in Blockchain / Solidity - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an enum in blockchain programming?

An enum is a special type that lets you define a set of named values. It helps you group related options together, like days of the week or transaction states.

beginner

Why use enums instead of plain numbers or strings?

Enums make code easier to read and less error-prone because you use meaningful names instead of numbers or strings. This helps prevent mistakes and makes your code clearer.

beginner

How do you define an enum for transaction status with values: Pending, Completed, Failed?

You write something like:<br>

enum TransactionStatus { Pending, Completed, Failed }

This groups the three states under one type.

intermediate

Can enums have underlying numeric values in blockchain languages?

Yes, enums often have underlying numbers starting from zero by default. You can also assign specific numbers if needed, which helps when storing or comparing values.

intermediate

How do enums improve smart contract security?

Enums limit possible values to a fixed set, reducing bugs from invalid inputs. This helps smart contracts behave predictably and safely.

What does an enum represent in blockchain programming?

A A function to send transactions

B A variable that changes randomly

C A fixed set of named values

D A type of cryptocurrency

Enums define a fixed set of named values to represent related options clearly.

Which of these is a correct enum definition for colors?

A enum Colors { Red, Green, Blue }

B enum Colors = (Red, Green, Blue)

C enum Colors: Red, Green, Blue

D enum Colors -> Red, Green, Blue

The correct syntax uses curly braces and commas to list enum values.

What is the default underlying value of the first enum member?

A 0

B 1

C Undefined

D Depends on the blockchain

By default, the first enum member has the numeric value 0.

How do enums help prevent bugs in smart contracts?

A By speeding up transactions

B By allowing any value to be used

C By encrypting data automatically

D By limiting values to a fixed set

Enums restrict values to a fixed set, reducing invalid inputs and bugs.

Can you assign specific numbers to enum members?

A No, enums only use default numbering

B Yes, you can assign specific numeric values

C Only strings can be assigned

D Only in off-chain code

You can assign specific numbers to enum members if you want custom values.

Explain what an enum is and why it is useful in blockchain programming.

Think about how enums help organize options like transaction states.

Describe how enums can improve the security and reliability of smart contracts.

Consider how limiting choices helps avoid mistakes.