Week 15: Advanced Design Patterns (Advanced)

Overview

Week 15 explores sophisticated design patterns that leverage Rust’s powerful type system. You’ll learn how to use advanced type-level programming techniques, zero-sized types, and state machines to create expressive, type-safe APIs. These patterns enable you to push more guarantees to compile time and reduce runtime errors.

Day 1-3: Rust-specific Design Patterns

Topics

  • RAII (Resource Acquisition Is Initialization) beyond basics:
    • Scoped resources
    • Nested RAII patterns
    • Cleanup guards
  • Type-state programming:
    • Encoding state in types
    • State transitions as type transformations
    • Preventing invalid states at compile time
  • Compile-time state machines:
    • Encoding state machines in the type system
    • Ensuring valid transitions at compile time
    • Using generics to model state transitions
  • The builder pattern in depth:
    • Required vs optional parameters
    • Type-safe builders
    • Validating configurations at compile time
  • The visitor pattern:
    • Implementing visitors with traits
    • Recursive visitors
    • Performance considerations
  • Composition over inheritance patterns
  • Function objects and higher-order functions
  • Type erasure techniques

Resources

Use Cases

  • API design for complex libraries
  • Creating foolproof interfaces
  • Building robust state machines
  • Resource management
  • Domain-specific languages (DSLs)
  • Configuration management
  • Ensuring invariants at compile time

Day 4-7: Advanced Type System Techniques

Topics

  • Zero-sized types (ZSTs):
    • Creating and using marker types
    • Optimizations with ZSTs
    • Type-level state with ZSTs
  • Phantom data and type markers:
    • Using PhantomData<T>
    • Type-level state tracking
    • Variance annotations
  • Type-level programming:
    • Type-level integers
    • Const generics
    • Type families
    • Leveraging the trait system for type-level computation
  • Generic Associated Types (GATs):
    • Using associated types with lifetime parameters
    • Higher-kinded types in Rust
    • Applications of GATs
  • Opaque types and impl Trait:
    • Return position impl Trait
    • Argument position impl Trait
    • type_alias_impl_trait feature
  • Advanced trait bounds:
    • Higher-ranked trait bounds (HRTB)
    • Negative trait bounds
    • Specialization (unstable)
  • Type-level macros and derive macros
  • The newtype pattern for type safety

Resources

Use Cases

  • Creating highly expressive APIs
  • Compile-time checked domain-specific languages
  • Implementing complex type-safe abstractions
  • Ensuring correctness at compile time
  • Creating deeply embedded domain models
  • Type-safe protocol implementations
  • Building self-documenting libraries

Exercises

  1. Implement a type-state builder pattern that prevents invalid object construction
  2. Create a compile-time state machine for a simple protocol
  3. Build a type-safe database query builder using advanced type techniques
  4. Implement a resource management system using RAII and cleanup guards
  5. Create a type-safe units library using type-level programming
  6. Build a type-safe task scheduler using GATs

Advanced Challenges

  1. Design and implement a type-safe parser combinator library
  2. Build a compile-time checked finite state machine
  3. Create a type-safe SQL query builder that prevents SQL injection
  4. Implement a session type system for enforcing protocol correctness
  5. Design a workflow engine with compile-time validation of workflow steps

Next Steps

After completing Week 15, you’ll have a deep understanding of advanced Rust design patterns and type-level programming. Week 16 will shift focus to systems programming by exploring FFI and C interoperability, allowing you to interface Rust with existing codebases and systems.