Crate lifetime[−][src]

Expand description

This crate provides traits and derive macros to change the lifetime of a type, allowing efficient reuse of your stucts or enums with any lifetime requirement.

`macros` feature

This crate’s macros are not enabled by default. Use the following in your Cargo.toml, replacing x.y with the version you want, to enable macros.

[dependencies]
lifetime = { version = "x.y", features = ["macros"] }

no_std

Use the following in your Cargo.toml, replacing x.y with the version you want, to disable the default std and alloc features.

[dependencies]
lifetime = { version = "x.y", default-features = false }

Examples

Note that the examples use explicit types and lifetimes to be more illustrative. Typically the lifetimes and/or types can be inferred by the compiler.

use lifetime::{IntoStatic, ToBorrowed};
use std::borrow::Cow;

let alice: Cow<'static, str> = Cow::Borrowed("Alice");

let borrowed_alice: Cow<'_, str> = alice.to_borrowed();
assert_eq!(borrowed_alice, alice);

let static_alice: Cow<'static, str> = borrowed_alice.into_static();
assert_eq!(static_alice, alice);

Here’s an example with a struct using the derive macros. The macros feature needs to be enabled.

use lifetime::{IntoStatic, ToBorrowed};
use std::borrow::Cow;

#[derive(IntoStatic, ToBorrowed)]
struct Header<'a> {
    name: Cow<'a, str>,
    value: Cow<'a, str>,
}

let xml: Header<'static> = Header {
    name: "content".into(),
    value: "xml".into(),
};
let mut xml_or_json: Header<'_> = xml.to_borrowed();
xml_or_json.value += " or json"; // creates a new String

assert_eq!(xml.value, "xml"); // xml header has not moved
assert_eq!(xml_or_json.value, "xml or json");

// IntoStatic converts all borrowed `&str` into `String`
let static_xml_or_json: Header<'static> = xml_or_json.into_static();
assert_eq!(static_xml_or_json.value, "xml or json");

Traits

IntoStatic

A trait for upgrading the lifetime of a type.

ToBorrowed

A trait for downgrading the lifetime of a type.

Derive Macros