How to read this book

Most pages are written as use cases. Each one starts from something you want to do in a game and shows how to do it with Rusteal:

• The goal: what the use case achieves in the game.
• The code: the Rust you write, complete enough to compile in a project made by rusteal new.
• In the editor: what you do in Unreal Editor, step by step, with the names the editor shows.
• Notes: limits, alternatives and what to watch for.

Code conventions

The examples import from two places:

• rusteal_runtime, the runtime crate: the attributes (uclass, uclass_impl, ustruct), the logging macro and the types every project uses (UObjectRef, RustealResult, OwnedStruct…).
• bindings, the crate Rusteal generates from your engine: one Rust type per engine class, struct and enum, grouped by engine module (bindings::engine, bindings::enhanced_input, bindings::ai…). bindings::prelude brings the common ones and the helper functions (bind_action, create_widget_of_class, FVector::from_dvec3…).

Engine names become Rust names in a fixed way. Classes lose their C++ prefix (AActor is Actor, UCharacterMovementComponent is CharacterMovementComponent); structs and enums keep it (FVector, ETriggerEvent); functions and properties are in snake_case (K2_GetActorLocation is k2_get_actor_location). A class’s functions come from a trait named after it with Ext at the end (ActorExt, CharacterMovementComponentExt), which you import with the class.

Optional parameters of engine functions, the ones with a default value in C++, are Options in Rust: Some(value) passes a value, None keeps the default.

Screenshots

Some steps are easier to follow with a picture of the editor. Where a picture belongs, the page has a placeholder like this one:

Screenshot: what the picture shows. (images/example.png)

The file name in parentheses is where the image goes, under src/images/.