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#27 in #multiple-values
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merge-rs
The merge
crate provides the Merge
trait that can be used to merge multiple
values into one:
trait Merge {
fn merge(&mut self, other: Self);
}
Merge
can be derived for structs:
use merge::Merge;
#[derive(Merge)]
struct User {
// Fields with the skip attribute are skipped by Merge
#[merge(skip)]
pub name: &'static str,
// The strategy attribute is used to select the merge behavior
#[merge(strategy = merge::option::overwrite_none)]
pub location: Option<&'static str>,
#[merge(strategy = merge::vec::append)]
pub groups: Vec<&'static str>,
}
let defaults = User {
name: "",
location: Some("Internet"),
groups: vec!["rust"],
};
let mut ferris = User {
name: "Ferris",
location: None,
groups: vec!["mascot"],
};
ferris.merge(defaults);
assert_eq!("Ferris", ferris.name);
assert_eq!(Some("Internet"), ferris.location);
assert_eq!(vec!["mascot", "rust"], ferris.groups);
A merge strategy is a function with the signature fn merge<T>(left: &mut T, right: T)
that merges right
into left
. The merge
crate provides
strategies for the most common types, but you can also define your own
strategies.
The trait can be used to merge configuration from different sources, for
example environment variables, multiple configuration files and command-line
arguments, see the args.rs
example.
Features
This crate has the following features:
derive
(default): Enables the derive macro for theMerge
trait using themerge_derive
crate.num
(default): Enables the merge strategies in thenum
module that require thenum_traits
crate.std
(default): Enables the merge strategies in thehashmap
andvec
modules that require the standard library. If this feature is not set,merge
is ano_std
library.
Minimum Supported Rust Version
This crate supports Rust 1.36.0 or later.
Contact
For bug reports, patches, feature requests and other messages, please send a
mail to ~ireas/public-inbox@lists.sr.ht (archive) using the
[merge-rs]
prefix in the subject.
You can submit patches using git send-email
, for example:
git send-email --to=~ireas/public-inbox@lists.sr.ht --subject-prefix="PATCH merge-rs"
Please prefix the subject with PATCH merge-rs
so that CI will be
automatically run.
License
This project is dual-licensed under the Apache-2.0 and MIT licenses.
The documentation and configuration files contained in this repository are
licensed under the Creative Commons Zero license. You can find a copy
of the license texts in the LICENSES
directory.
merge-rs
complies with version 3.0 of the REUSE specification.
Dependencies
~0–275KB