projects / rustc.git / blame
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|---|---|---|
| 8bb4bdeb XL |
1 | lazy-static.rs |
| 2 | ============== | |
| 3 | ||
| 4 | A macro for declaring lazily evaluated statics in Rust. | |
| 5 | ||
| 6 | Using this macro, it is possible to have `static`s that require code to be | |
| 7 | executed at runtime in order to be initialized. | |
| 8 | This includes anything requiring heap allocations, like vectors or hash maps, | |
| 9 | as well as anything that requires non-const function calls to be computed. | |
| 10 | ||
| 11 | [](https://travis-ci.org/rust-lang-nursery/lazy-static.rs) | |
| 12 | ||
| 13 | # Getting Started | |
| 14 | ||
| 15 | [lazy-static.rs is available on crates.io](https://crates.io/crates/lazy_static). | |
| 16 | It is recommended to look there for the newest released version, as well as links to the newest builds of the docs. | |
| 17 | ||
| 18 | At the point of the last update of this README, the latest published version could be used like this: | |
| 19 | ||
| 20 | Add the following dependency to your Cargo manifest... | |
| 21 | ||
| 22 | ```toml | |
| 23 | [dependencies] | |
| 24 | lazy_static = "0.2" | |
| 25 | ``` | |
| 26 | ||
| 27 | ...and see the [docs](http://rust-lang-nursery.github.io/lazy-static.rs/lazy_static/index.html) for how to use it. | |
| 28 | ||
| 29 | # Example | |
| 30 | ||
| 31 | ```rust | |
| 32 | #[macro_use] | |
| 33 | extern crate lazy_static; | |
| 34 | ||
| 35 | use std::collections::HashMap; | |
| 36 | ||
| 37 | lazy_static! { | |
| 38 | static ref HASHMAP: HashMap<u32, &'static str> = { | |
| 39 | let mut m = HashMap::new(); | |
| 40 | m.insert(0, "foo"); | |
| 41 | m.insert(1, "bar"); | |
| 42 | m.insert(2, "baz"); | |
| 43 | m | |
| 44 | }; | |
| 45 | } | |
| 46 | ||
| 47 | fn main() { | |
| 48 | // First access to `HASHMAP` initializes it | |
| 49 | println!("The entry for `0` is \"{}\".", HASHMAP.get(&0).unwrap()); | |
| 50 | ||
| 51 | // Any further access to `HASHMAP` just returns the computed value | |
| 52 | println!("The entry for `1` is \"{}\".", HASHMAP.get(&1).unwrap()); | |
| 53 | } | |
| 54 | ``` | |
| 7cac9316 XL |
55 | |
| 56 | ## License | |
| 57 | ||
| 58 | Licensed under either of | |
| 59 | ||
| 60 | * Apache License, Version 2.0, ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0) | |
| 61 | * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT) | |
| 62 | ||
| 63 | at your option. | |
| 64 | ||
| 65 | ### Contribution | |
| 66 | ||
| 67 | Unless you explicitly state otherwise, any contribution intentionally submitted | |
| 68 | for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any | |
| 69 | additional terms or conditions. |