# Struct Patch
[![Crates.io][crates-badge]][crate-url]
[![MIT licensed][mit-badge]][mit-url]
[![Docs][doc-badge]][doc-url]
A lib help you patch Rust instance, and easy to partial update configures.
## Introduction
This crate provides the `Patch` trait and an accompanying derive macro.
Deriving `Patch` on a struct will generate a struct similar to the original one, but with all fields wrapped in an `Option`.
An instance of such a patch struct can be applied onto the original struct, replacing values only if they are set to `Some`, leaving them unchanged otherwise.
## Quick Example
```rust
use struct_patch::Patch;
use serde::{Deserialize, Serialize};
#[derive(Default, Debug, PartialEq, Patch)]
#[patch_derive(Debug, Default, Deserialize, Serialize)]
struct Item {
field_bool: bool,
field_int: usize,
field_string: String,
}
fn patch_json() {
let mut item = Item {
field_bool: true,
field_int: 42,
field_string: String::from("hello"),
};
let data = r#"{
"field_int": 7
}"#;
let patch: ItemPatch = serde_json::from_str(data).unwrap();
item.apply(patch);
assert_eq!(
item,
Item {
field_bool: true,
field_int: 7,
field_string: String::from("hello")
}
);
}
```
[crates-badge]: https://img.shields.io/crates/v/struct-patch.svg
[crate-url]: https://crates.io/crates/struct-patch
[mit-badge]: https://img.shields.io/badge/license-MIT-blue.svg
[mit-url]: https://github.com/yanganto/struct-patch/blob/readme/LICENSE
[doc-badge]: https://img.shields.io/badge/docs-rs-orange.svg
[doc-url]: https://docs.rs/struct-patch/