10 Protobuf Enum Best Practices

Protocol Buffers (Protobuf) is a popular data serialization format used in many applications. It is a language-neutral, platform-neutral, extensible way of serializing structured data for use in communications protocols, data storage, and more.

One of the most important aspects of Protobuf is the use of enums. Enums are a way of defining a set of named constants that can be used to represent a set of values. In this article, we will discuss 10 best practices for using enums in Protobuf. We will cover topics such as naming conventions, versioning, and more.

1. Use a reserved range for internal values

When you use a reserved range for internal values, it allows you to add new enum values without breaking existing code. This is because the reserved range will not be used by any external clients and therefore won’t affect their code. It also makes it easier to maintain your protobuf enums since you can easily identify which values are intended for internal use only.

Using a reserved range for internal values also helps ensure that your protobuf enums remain consistent across different versions of your application. By reserving a range of values, you can guarantee that no matter how many times you update your application, those values will always stay the same.

2. Use the same enum in multiple messages

By using the same enum in multiple messages, you can ensure that all of your messages are consistent and up-to-date. This makes it easier to maintain and debug your code since you don’t have to worry about different versions of the same enum being used in different messages. Additionally, this practice helps keep your codebase more organized and readable by avoiding duplicate enums.

3. Don’t use enums to represent flags

Enums are meant to represent a single value, and when you use them to represent flags, it can lead to confusion. For example, if you have an enum with values A, B, C, D, and E, and you want to represent the combination of A and B as one flag, then using enums would not be ideal because there is no way to represent that combination in a single enum value.

Instead, it’s better to use bit fields or other data structures to represent multiple flags. This will make your code more readable and maintainable, and it will also help avoid any potential confusion.

4. Avoid using enums with many values

Enums with many values can be difficult to maintain and debug. If you have an enum with too many values, it’s likely that the code will become cluttered and hard to read. Additionally, if a new value is added or removed from the enum, all of the existing code must be updated accordingly.

To avoid this problem, try to limit your enums to no more than 10-15 values. This way, you’ll be able to keep track of them easily and make sure they are up to date. You should also consider using flags instead of enums when possible, as this allows for multiple values to be set at once.

5. Enum names should be singular, not plural

When you use a plural name for an enum, it can be confusing to read and understand the code. For example, if you have an enum called “colors” with values like “red”, “blue”, and “green”, it’s not immediately clear what each value represents. Is it a single color or multiple colors?

By using singular names instead, such as “color”, it becomes much clearer that each value is a single color. This makes your code easier to read and understand, which in turn makes it easier to maintain and debug.

6. Prefer numeric values over symbolic ones

Numeric values are more efficient to encode and decode, as they require fewer bytes than symbolic ones. This means that your messages will be smaller in size, which can lead to faster transmission times and lower bandwidth costs. Additionally, numeric values are easier to debug since you don’t have to look up the meaning of each symbol.

Finally, it’s important to note that Protobuf enums are not extensible. If you use symbolic values, then adding new enum values requires changing all existing code. On the other hand, if you use numeric values, then you can add new enum values without having to change any existing code.

7. Define an UNKNOWN value

When you define an enum in protobuf, it is possible for a message to contain a value that isn’t defined in the enum. This can happen if the sender and receiver are using different versions of the same protocol. If this happens, your application won’t be able to interpret the data correctly.

By defining an UNKNOWN value in your enum, you can ensure that any unexpected values will be handled gracefully. The UNKNOWN value should always have the highest numerical value in the enum so that it’s easy to identify when it’s encountered.

8. Consider defining a DEFAULT value

When using protobuf enums, it’s important to consider the possibility that a message may be received with an unknown enum value. In this case, having a DEFAULT value defined in your code can help you handle these cases gracefully and avoid unexpected errors or crashes.

The DEFAULT value should be set to something that makes sense for your application. For example, if you’re defining an enum for user roles, then setting the DEFAULT value to “USER” would make sense. This way, any messages received with an unknown role will still be handled correctly by your application.

9. Ensure that your default value is valid

When you define an enum in protobuf, the compiler will automatically assign a numerical value to each of your enum values. This means that if you don’t specify a default value for your enum, it will be assigned the numerical value 0.

However, this can lead to problems because 0 is often used as a placeholder or invalid value. To avoid this issue, make sure to always explicitly set a default value for your enums. That way, you’ll know that any time you encounter a 0 value, it’s intentional and not just a placeholder.

10. Make sure you can detect when a field has been cleared

When a field is cleared, it’s important to know that the value has been reset. This helps you avoid any potential errors or bugs in your code. To do this, make sure you use an enum type with a special “cleared” value. That way, when the field is cleared, the enum will be set to the “cleared” value and you can detect it easily.

It’s also important to make sure that all of your enums are properly documented so that other developers understand what each value means. This will help ensure that everyone is on the same page and that no mistakes are made.