[−][src]Crate merge
Provides Merge
, a trait for objects that can be merged.
Usage
trait Merge { fn merge(&mut self, other: Self); }
The Merge
trait can be used to merge two objects of the same type into one. The intended
use case is merging configuration from different sources, for example environment variables,
multiple configuration files and command-line arguments, see the args.rs
example.
Merge
is implemented for Option
and can be derived for structs. When deriving the Merge
trait for a struct, you can provide custom merge strategies for the fields that don’t implement
Merge
. A merge strategy is a function with the signature fn merge<T>(left: &mut T, right: T)
that merges right
into left
. The submodules of this crate provide strategies for the
most common types, but you can also define your own strategies.
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 thevec
module that require the standard library. If this feature is not set,merge
is ano_std
library.
Example
use merge::Merge; #[derive(Merge)] struct User { // Fields with the skip attribute are skipped by Merge #[merge(skip)] pub name: &'static str, // The Merge implementation for Option replaces its value if it is None pub location: Option<&'static str>, // The strategy attribute is used to customize the merge behavior #[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);
Modules
bool | Merge strategies for boolean types. |
num | Merge strategies for numeric types. |
ord | Merge strategies for types that form a total order. |
vec | Merge strategies for vectors. |
Traits
Merge | A trait for objects that can be merged. |
Derive Macros
Merge |