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# Traits
A `trait` is a collection of methods defined for an unknown type:
`Self`. They can access other methods declared in the same trait.
Traits can be implemented for any data type. In the example below,
we define `Animal`, a group of methods. The `Animal` `trait` is
then implemented for the `Sheep` data type, allowing the use of
methods from `Animal` with a `Sheep`.
```rust,editable
struct Sheep { naked: bool, name: &'static str }
trait Animal {
// Associated function signature; `Self` refers to the implementor type.
fn new(name: &'static str) -> Self;
// Method signatures; these will return a string.
fn name(&self) -> &'static str;
fn noise(&self) -> &'static str;
// Traits can provide default method definitions.
fn talk(&self) {
println!("{} says {}", self.name(), self.noise());
}
}
impl Sheep {
fn is_naked(&self) -> bool {
self.naked
}
fn shear(&mut self) {
if self.is_naked() {
// Implementor methods can use the implementor's trait methods.
println!("{} is already naked...", self.name());
} else {
println!("{} gets a haircut!", self.name);
self.naked = true;
}
}
}
// Implement the `Animal` trait for `Sheep`.
impl Animal for Sheep {
// `Self` is the implementor type: `Sheep`.
fn new(name: &'static str) -> Sheep {
Sheep { name: name, naked: false }
}
fn name(&self) -> &'static str {
self.name
}
fn noise(&self) -> &'static str {
if self.is_naked() {
"baaaaah?"
} else {
"baaaaah!"
}
}
// Default trait methods can be overridden.
fn talk(&self) {
// For example, we can add some quiet contemplation.
println!("{} pauses briefly... {}", self.name, self.noise());
}
}
fn main() {
// Type annotation is necessary in this case.
let mut dolly: Sheep = Animal::new("Dolly");
// TODO ^ Try removing the type annotations.
dolly.talk();
dolly.shear();
dolly.talk();
}
```
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