README.md

Enums and Pattern Matching¹

To run the program:

$ cargo run --bin enums-patterns
   Compiling enums-patterns v0.1.0 ...

Lessons learned

As I have some prior experience with enums and pattern matching from other languages (Ruby, OCaml, etc), the lessons learned here will be briefer than other sections.

Defining an enum is easy:

enum IpAddressKind {
    V4,
    V6,
}

They are extra powerful when they contain semantic data:

enum IpAddress {
    V4(u8, u8, u8, u8),
    V6(String),
}

To retrieve values, use match:

match ip_address {
  V4(a, b, c, d) => println!("{a}.{b}.{c}.{d}"),
  V6(e) => println!("{e}"),
}

Or, use if let to handle a single case:

if let V4(a, b, c, d) = ip_address {
  println!("{a}.{b}.{c}.{d}");
}

Footnotes

1. Source: https://doc.rust-lang.org/book/ch06-00-enums.html ↩