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https://github.com/estebank/makeit
Zero-overhead type-safe builder pattern `derive` macro for your Rust structs
https://github.com/estebank/makeit
Last synced: 14 days ago
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Zero-overhead type-safe builder pattern `derive` macro for your Rust structs
- Host: GitHub
- URL: https://github.com/estebank/makeit
- Owner: estebank
- Created: 2022-02-14T19:03:09.000Z (over 2 years ago)
- Default Branch: main
- Last Pushed: 2023-06-03T21:39:11.000Z (over 1 year ago)
- Last Synced: 2024-09-18T09:08:18.060Z (about 2 months ago)
- Language: Rust
- Size: 15.6 KB
- Stars: 222
- Watchers: 4
- Forks: 11
- Open Issues: 8
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Metadata Files:
- Readme: README.md
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README
# Compile-time checked Builder pattern `derive` macro with zero-memory overhead
> *This is very much a work-in-progress. PRs to bring this to production quality are welcome.*
The [Builder Pattern](https://en.wikipedia.org/wiki/Builder_pattern) is a design pattern to allow the construction of complex types one field at a time by calling methods on a builder type. This crate provides a `derive` macro that allows you to annotate any `struct` to create a type-level state machine that requires all mandatory fields to be set once and only at compile-time (otherwise you won't be able to call `.build()` on it).
```rust
use makeit::{Buildable, Builder};
#[derive(Builder)]
struct Foo<'a, T: std::fmt::Debug> {
bar: &'a T,
#[default(42)]
baz: i32,
}
// This is the expected use
let x = Foo::builder().set_bar(&()).set_baz(42).build();
// The following builds because of the `default` annotation on `baz`
let x = Foo::builder().set_bar(&()).build();
// The following won't build because `bar` hasn't been set
let x = Foo::builder().set_baz(0).build();
```
You can look at the `examples` directory for a showcase of the available features.
The created `Builder` type has zero-memory overhead because it uses a [`MaybeUninit` backed field](https://lucumr.pocoo.org/2022/1/30/unsafe-rust/) of the type to be built.
## Error messages
One of the main downsides of the typestate pattern are inscrutable error messages. However, the since this crate generates type-state parameters with readable names, rustc can produce readable error messages:
