Rust: What is the difference between struct and enum?

Struct — custom type with fields (single shape). Enum — type with multiple variants.

Struct:

• Defines a type where all fields exist together.
• Three forms: named fields, tuple structs, unit structs.
• Methods defined in impl blocks.
• Represents "this thing has these properties."

1struct Player {
2    name: String,
3    score: u32,
4    active: bool,
5}
6
7impl Player {
8    fn new(name: &str) -> Self {
9        Self { name: name.to_string(), score: 0, active: true }
10    }
11}

Enum:

• Defines a type that can be one of several variants.
• Variants can hold different data.
• Pattern matching with match ensures all cases handled.
• Represents "this thing is one of these."

1enum Direction {
2    North,
3    South,
4    East,
5    West,
6}
7
8fn turn(dir: Direction) -> Direction {
9    match dir {
10        Direction::North => Direction::East,
11        Direction::East => Direction::South,
12        Direction::South => Direction::West,
13        Direction::West => Direction::North,
14    }
15}

When to use:

• Structs for data containers with fixed fields.
• Enums when a value can be one of several kinds.
• Enums for state machines and domain modeling.

Common mistakes:

• Forgetting a variant in match — compiler enforces exhaustiveness.
• Using enums when all variants have the same fields — structs are simpler.
• Not deriving common traits like Debug, Clone.