merge

Trait Merge

Source 
pub trait Merge {
    // Required method
    fn merge(&mut self, other: Self);
}
Expand description

A trait for objects that can be merged.

§Deriving

Merge can be derived for structs if the derive feature is enabled. The generated implementation calls the merge method for all fields, or the merge strategy function if set. You can use these field attributes to configure the generated implementation:

  • skip: Skip this field in the merge method.
  • strategy = f: Call f(self.field, other.field) instead of calling the merge function for this field.

You can also set a default strategy for all fields by setting the strategy attribute for the struct.

§Examples

Deriving Merge for a struct:

use merge::Merge;

#[derive(Debug, PartialEq, Merge)]
struct S {
    #[merge(strategy = merge::option::overwrite_none)]
    option: Option<usize>,

    #[merge(skip)]
    s: String,

    #[merge(strategy = merge::bool::overwrite_false)]
    flag: bool,
}

let mut val = S {
    option: None,
    s: "some ignored value".to_owned(),
    flag: false,
};
val.merge(S {
    option: Some(42),
    s: "some other ignored value".to_owned(),
    flag: true,
});
assert_eq!(S {
    option: Some(42),
    s: "some ignored value".to_owned(),
    flag: true,
}, val);

Setting a default merge strategy:

use merge::Merge;

#[derive(Debug, PartialEq, Merge)]
#[merge(strategy = merge::option::overwrite_none)]
struct S {
    option1: Option<usize>,
    option2: Option<usize>,
    option3: Option<usize>,
}

let mut val = S {
    option1: None,
    option2: Some(1),
    option3: None,
};
val.merge(S {
    option1: Some(2),
    option2: Some(2),
    option3: None,
});
assert_eq!(S {
    option1: Some(2),
    option2: Some(1),
    option3: None,
}, val);

Required Methods§

Source

fn merge(&mut self, other: Self)

Merge another object into this object.

Dyn Compatibility§

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors§