Lessons
Traits and trait bounds
Defining traits, implementing traits, default methods, impl Trait parameters, and dyn Trait objects.
Prerequisite: Foundations track complete
What to look for:
- impl Animal for Dog — concrete implementation
- trait default methods — can be overridden
- impl Trait vs T: Trait — same thing, cleaner syntax
- dyn Trait — fat pointer, runtime dispatch, heap allocation needed
Generics and standard library traits
Generic functions and structs, T: Trait bounds, derive macros, Display, Clone, Iterator.
Prerequisite: Lesson 1 of Practitioner
What to look for:
- The standard traits table — Debug, Clone, PartialEq, Hash
- #[derive] generates these automatically
- Monomorphisation: zero-cost, each type gets its own compiled code
- impl Display for custom types
Closures and iterators
Closure syntax, capturing environment, Fn/FnMut/FnOnce traits, iterator adapters, and collect.
Prerequisite: Lesson 2 of Practitioner
What to look for:
- |x| x * 2 closure syntax
- Closures capture by reference by default, or by value with move
- Iterator: map, filter, take, zip, flatten, collect
- iter() vs into_iter() vs iter_mut()
Error handling and the ? operator
Custom error types with From conversions, thiserror crate pattern, and anyhow for application code.
Prerequisite: Lesson 3 of Practitioner
What to look for:
- From
- map_err() to convert error types inline
- Exploring tab: the full custom error type pattern
- When to use Box
(quick scripts) vs custom enums (libraries)
Collections: Vec, HashMap, String
Vec
Prerequisite: Lesson 4 of Practitioner
What to look for:
- vec![1,2,3] macro
- HashMap::entry().or_insert() — idiomatic insert-or-update
- String::from() vs to_string() vs &str
- Iterating: for s in &v vs for s in v (consumes v)
How to use this track: Each lesson links to the Codex Rust reference page. Use reading level tabs. Rust borrow checker errors are the lesson — read them carefully. Practice at play.rust-lang.org.
Track quiz
4 questions to check your understanding.
What is the difference between impl Trait and dyn Trait in function parameters?
What does #[derive(Debug)] do?
What does iterator.collect::
In Rust, what does map_err() do on a Result?