CODEWITHSUNDEEP
rusttrait-objects
Divyansh
Divyansh

Reputation: 67

Is there any way to use Associated Function of a trait in Rust?

I was experimenting with associated functions inside a trait's implementation, in order to use the trait's original implementation of the function. But I can't find a way to do that. My experimentation code :

pub trait T1 {
    // note: trait items always share the visibility of their methods.
    fn new() -> String {
        return String::new();
    }
}

pub enum X_type {
    String,
}

struct T1_1 {
    buddy: String,
}

impl T1 for T1_1 {}

fn main() {
    println!("{}", <dyn T1 as T1>::new());
}

Link to the playground.

I have tried tweaking the code here and there to see if T1::new() can be used, but it does not seem possible.

Upvotes: 1

Views: 142

Answers (1)

Unlikus
Unlikus

Reputation: 1858

If you try T1::new() the compiler will actually tell you what to do:

error[E0790]: cannot call associated function on trait without specifying the corresponding `impl` type
  --> src/main.rs:19:20
   |
3  | /     fn new() -> String {
4  | |         return String::new();
5  | |     }
   | |_____- `T1::new` defined here
...
19 |       println!("{}", T1::new());
   |                      ^^^^^^^^^ cannot call associated function of trait
   |
help: use the fully-qualified path to the only available implementation
   |
19 |     println!("{}", <T1_1 as T1>::new());
   |                    ++++++++   +

This is because there can be different implementation for T1::new() for each type which implements this trait, so you should specify which implementation you want.

Upvotes: 0

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