Type state
The typestate pattern encodes an object's valid states and permitted operations or transitions in its types, allowing invalid uses to be rejected by the type system.
Write Powerful Rust Macros
The type state pattern encodes an object's permitted states in its type so invalid state transitions or configurations are rejected at compile time.
- How it is used
- Enforces required builder fields and valid state transitions before construction or final macro output.
- How deep it goes
- Works through marker traits, generic state parameters, PhantomData, generated transition methods, and compile-fail testing for a builder.
- Examples
- Uses a red/green traffic light, a Gleipnir builder with three required fields, and a missing-field compile-fail test.
- What you can do after
- Build it from scratch by generating state-specific builders whose final state alone exposes `build`.
Idiomatic Rust
A type-safe state machine is a state-machine design whose valid states and transitions are enforced by the programming language's type system.
- How it is used
- Uses type-level states to keep software and external state aligned and make invalid transitions unavailable.
- How deep it goes
- Defines states and transitions and demonstrates state-specific methods; omits database lookup and validation during session resumption.
- Examples
- Demonstrates light-bulb transitions and a user session with authentication, property updates, and logout.
- What you can do after
- Build a Rust state machine whose state-specific methods and transitions are checked by the type system.
Related concepts
- genericsuses · Generics are programming-language constructs that parameterize or generalize types and operations so they can apply to multiple concrete types or input forms.
- builder patternused by · The builder pattern is a creational design pattern that constructs a complex object through separate, stepwise configuration and assembly operations.
- illegal stateaddresses · An illegal state is a program or system state that violates constraints required by its data model, domain rules, or specification.
- finite-state machinekind of · A finite-state machine is a computational model with a finite set of states and defined transitions that govern changes of state in response to inputs, events, or conditions.
- compilation testmeasured by · A compilation test checks whether source code, including a macro invocation, compiles successfully or fails as expected.
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