join vector of non-strings into a string rust - rust

Question

I have a type T that implements display (so it has a .to_string() method)
let my_vec = vec![T(), T(), T()];
println!("{}", my_vec.join(", "));
sadly errors with "trait bounds not satisfied" because the separator, ", ", is not of the same type as the vector's items (I'm pretty sure).
I guess my workaround is then
println!("{}", my_vec.iter().map(|x| x.to_string()).collect::<Vec<_>>().join(", "));
But isn't there anything shorter and clearer that I can write out instead of this?
I've just written this function to help me out:
fn join<T, I>(vec: &[T], sep: I) -> String
where
T: std::fmt::Display,
I: std::fmt::Display,
{
vec.iter().map(|x| x.to_string()).collect::<Vec<_>>().join(&sep.to_string())
}
But I'd rather not have to. There must be alternative solutions that: are already built-in, don't require manual implementation, at least don't require the creation of a top-level function that's then only called twice.

Answer 1

AFAIK, your work around is good and sound without non-std libs.
Several cargos provide some helper functions for this issue, for example:
Playground
itertools and joinery
use itertools::Itertools;
use joinery::Joinable;
struct Color {
red: u8,
green: u8,
blue: u8,
}
impl std::fmt::Display for Color {
fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
write!(
f,
"RGB ({}, {}, {}) 0x{:02X}{:02X}{:02X}",
self.red, self.green, self.blue, self.red, self.green, self.blue
)
}
}
fn main() {
let colors = vec![
Color {
red: 128,
green: 255,
blue: 90,
},
Color {
red: 0,
green: 3,
blue: 254,
},
];
println!(
"{}",
colors
.iter()
.map(|x| x.to_string())
.collect::<Vec<_>>()
.join(", ")
);
println!("{}", colors.iter().join(", "));
println!("{}", colors.join_with(", "));
}