I have this code:
fn func<T, U>(f: T) where T: Fn()-> U, U: MyTrait {
let state = f();
// ...
}
f here is just a new function from a trait MyTrait for some struct. I want to have a function which works with every struct implementing MyTrait, and there is new method for that trait I want to call for state.
How can I pass the struct (not a value with type of that struct) into a function with restriction on the specific trait been implemented for that struct?
You do not need to pass any parameter; the type parameter U you already have is all you need.
fn func<U>(...)
where
U: MyTrait
{
...
let state = U::new();
...
}
Or did you mean you want a generic implementation of just Fn() -> U? That's even easier: U::new is already that. Example using Default as the trait, but you can use any trait in the same way:
use std::fmt::Debug;
fn print_instance<T: Debug, F: Fn() -> T>(f: F) {
println!("{:?}", f());
}
fn print_default<T: Debug + Default>() {
print_instance::<T, _>(Default::default);
}
fn main() {
print_default::<Vec<i32>>();
print_default::<f32>();
}
(...), but yes, it's here.
new()that you want to call in yourfun()?fn func<T: MyTrait>(arg: T){let state = T::new();}arg: Tis a function here, and I want to pass the type to use.