Rust Design Patterns

An open source repository of design patterns and idioms in the Rust programming language.

Contents

Introduction

Idioms

• Constructor
• Concatenating strings with format!
• private field to indicate extensibility
• trait to separate visibility of methods from visibility of data (https://github.com/sfackler/rust-postgres/blob/master/src/lib.rs#L1400)
• Deref on Vec/String to treat like a smart pointer/borrowed view of such data
• leak amplification ("Vec::drain sets the Vec's len to 0 prematurely so that mem::forgetting Drain "only" mem::forgets more stuff. instead of exposing uninitialized memory or having to update the len on every iteration")
• dtor for finally
• interior mutability - UnsafeCell, Cell, RefCell
• treating Option like a list

Design patterns

• Builder
• RAII ( + borrows - mutex guard)
• newtype (can be used to restrict functionality, make by-move rather than by-copy, abstraction, e.g., https://github.com/rust-lang/rust/blob/master/src/libcore/str/mod.rs#L366-L372)
• iterators (to safely avoid bounds checks)
• closures and lifetimes (coupling to lifetime)
• platform-specific sub-modules (https://github.com/rust-lang/rfcs/blob/master/text/0517-io-os-reform.md#platform-specific-opt-in)
• affine types/session types
• Entry API vs insert_or_update etc.
• visitor
• fold
• small crates and semver
• extension traits
• destructor bombs (ensure linear typing dynamically, e.g., 0f25ccb7c3)
• convertible to Foo trait for more generic generics (e.g., http://static.rust-lang.org/doc/master/std/fs/struct.File.html#method.open)
• late binding of bounds for better APIs (i.e., Mutex's don't require Send)
• 'shadow' borrowed version of struct - e.g., double buffering, Niko's parser generator
• composition of structs to please the borrow checker

Anti-patterns

• thread + catch_panic for exceptions
• Clone to satisfy the borrow checker
• Deref polymorphism
• Matching all fields of a struct (back compat)
• wildcard matches
• tkaing an enum rather than having multiple functions

Contributing

Contributions are very welcome!

You should start with the template. Copy it into the appropriate directory, edit it, and submit a PR. You might not want every section, and you might want to add extra sections.

Correction and elaboration PRs are very welcome.