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50 lines
1.4 KiB
Markdown
50 lines
1.4 KiB
Markdown
# Trait bound Typemap [](https://crates.io/crates/trait-bound-typemap) [](https://docs.rs/trait-bound-typemap)
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This crate offers typemaps that restrict a given type in their
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trait and therefore offer additional trait implementations such as `Clone` and `PartialEq`.
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## Safety
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This crate relies on the [multi-trait-object](https://crates.io/crates/multi-trait-object) crate
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which provides a workaround for storing a type erased object with all associated traits until
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this feature is implemented in the language itself. This crate will likely break when the
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fat pointer used by trait objects changes which it hasn't in a long time so far.
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## Usage
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```rust
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use trait_bound_typemap::{CloneTypeMap, AnyTypeMap, TypeMapTrait, TypeMapKey};
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#[derive(Clone)]
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pub struct MyStruct {
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a: u8,
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b: String,
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}
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pub struct MyStructKey;
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impl TypeMapKey for MyStructKey {
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type Value = MyStruct;
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}
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fn main() {
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let mut map = CloneTypeMap::new();
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let value = MyStruct {a: 5, b: String::from("Hello World")};
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map.insert::<MyStructKey>(value);
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assert!(map.contains_key::<MyStructKey>());
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// can be cloned
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let map2 = map.clone();
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assert!(map.contains_key::<MyStructKey>());
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// less restrictive is always allowed
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let any_map = AnyTypeMap::from_iter(map2);
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assert!(map.contains_key::<MyStructKey>());
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}
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```
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## License
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Apache-2.0 |