Enums in Solidity

The most intuitive solutions—like using strings or plain numbers—may seem simple at first, but in the world of smart contracts, they hide huge pitfalls. These approaches can either waste gas or hurt code readability and maintainability.

Fortunately, Solidity provides an elegant and efficient solution: enums. This article uncovers three key insights about enums that will help you write clearer and more efficient smart contracts.

1. The Simple Trap

When choosing how to represent states, developers often fall into two common traps: using strings or “magic numbers.” Let’s see why both are bad choices in Solidity.

The String Problem

Using strings like "pending" feels natural, but it has major downsides:

• String operations are expensive in Solidity.
• Comparisons are inefficient.
• Storing and managing them burns gas unnecessarily.

The Magic Number Problem

Another approach is to use integers to represent states:

• 1 → pending
• 2 → shipped
• 3 → delivered

While this is more gas-efficient, it destroys readability:

In short:

• Strings → costly for users (gas).
• Numbers → costly for developers (maintainability). Both are unacceptable in smart contract design.

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2. The Best of Both Worlds: Enum’s Readability and Efficiency

Enums solve both of these problems at once, providing clarity for developers and efficiency for the EVM.

Core Concept

An enum lets you define a custom type with a fixed set of named values. For example:

enum Status {
    Pending,
    Shipped,
    Delivered
}

Dual Advantages

1. For developers: Enums make code self-explanatory.
   if (status == Status.Delivered) { ... }
   is infinitely clearer than status == 2.

2. For the EVM: Under the hood, enums are just unsigned integers.

Pending = 0

Shipped = 1

Delivered = 2

Enums combine human readability with machine efficiency, making them the go-to tool for state management.

Conclusion

Enums are far more than syntactic sugar—they’re a fundamental building block for writing clear, safe, and efficient Solidity code.

If you’re writing smart contracts, mastering enums is not optional—it’s essential.