Structs and enums

Last reviewed May 28, 2026 Content v20260528

Track mode: server_compiled
Means: Compiled runner
Reading: ~1 min
Level: beginner

This lesson

This lesson teaches Structs and enums: the syntax, APIs, and habits you need before advancing in Rust.

Teams ship Structs and enums on every Rust codebase—skipping it leaves gaps in debugging and code reviews.

You will apply Structs and enums in contexts like: Infrastructure CLIs, proxies, game engines, blockchain nodes, and latency-sensitive backends.

Write Rust with fn main(), click Run on server—the dev runner compiles main.rs with rustc and runs the binary; fix borrow errors from stderr (requires Rust toolchain; LEARNING_RUNNER_ENABLED=true).

When you can explain the previous lesson's ideas without copying starter code.

Structs group named fields. Enums define variants—optionally carrying data. Rust enums are algebraic sum types, richer than C-style enums.

Struct example

struct User { name: String, active: bool }

Enum example

enum Status { Draft, Published }

Self-check

What keyword defines a product type with fields?
Can enum variants hold data?

Tuple and unit structs

Tuple structs wrap a single field (struct Meters(f64)) for newtype safety. Unit variants like Option::None model absence without null pointers.

Compare to Go: Rust enums with data replace interface{} + type switches for many API shapes.

Interview tip Lesson completion confidence

Can you explain this lesson in 30 seconds without reading notes?

Self-reflection (saved on this device)

Not saved yet.

Playground

Runs on the configured server runner (dev: npm run runner with LEARNING_RUNNER_ENABLED=true). Output appears below the editor.

Code runner not available

Server runner is disabled. Set LEARNING_RUNNER_ENABLED=true and LEARNING_RUNNER_URL in .env (see .env.example).

Check yourself

Multiple choice — immediate feedback.

Discussion

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Starter discussion topics

Tuple struct when?
Enum vs trait?

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