When I try to call a trait method on a function pointer:
trait Foo {
fn do_it(&self, i: i32);
}
impl Foo for fn(i32) {
fn do_it(&self, i: i32) {
self(i)
}
}
fn bar(i: i32) {}
fn baz() {
bar.do_it(7);
}
The compiler says no method named 'do_it' found for fn item 'fn(i32) {bar}' in the current scope ... note: 'Foo' defines an item 'do_it', perhaps you need to implement it.
What's wrong with my implementation?
You need to impl Foo on a trait object, instead of trying to access the fn() type. By declaring that you want to implement Foo for any object F which has already implemented the Fn(i32) trait, the compiler then recognizes that there is a method associated with that type of function.
I added main() to be able to view output and verify it worked as expected.
trait Foo {
fn do_it(&self, i: i32);
}
impl<F> Foo for F where F: Fn(i32) {
fn do_it(&self, i: i32) {
self(i)
}
}
fn bar(i: i32) {
println!("{}", i);
}
fn main() {
bar.do_it(7);
}
dyn Fn here. This is so-called "blanket implementation" - doc.rust-lang.org/book/….
