صفات مرزی (Trait Bounds)

When working with generics, you often want to require the types to implement some trait, so that you can call this trait’s methods.

You can do this with T: Trait or impl Trait:

fn duplicate<T: Clone>(a: T) -> (T, T) {
    (a.clone(), a.clone())
}

// struct NotClonable;

fn main() {
    let foo = String::from("foo");
    let pair = duplicate(foo);
    println!("{pair:?}");
}

This slide should take about 8 minutes.

Try making a NonClonable and passing it to duplicate.
When multiple traits are necessary, use + to join them.
Show a where clause, students will encounter it when reading code.
```
fn duplicate<T>(a: T) -> (T, T)
where
    T: Clone,
{
    (a.clone(), a.clone())
}
```
- It declutters the function signature if you have many parameters.
- It has additional features making it more powerful.
  - If someone asks, the extra feature is that the type on the left of “:” can be arbitrary, like Option<T>.
Note that Rust does not (yet) support specialization. For example, given the original duplicate, it is invalid to add a specialized duplicate(a: u32).

Comprehensive Rust 🦀

صفات مرزی (Trait Bounds)