Vec of objects implementing generic trait [duplicate] - rust

Question

This question already has answers here:
How can I have a collection of objects that differ by their associated type?
(3 answers)
Vector of objects belonging to a trait
(3 answers)
Closed 4 years ago.
I am building a command-line application. I have the following trait:
trait ValidatedCommand {
type Output;
fn run() -> Result<Self::Output, std::io::Error>;
}
and I have the following two implementations for it:
struct First;
impl ValidatedCommand for First {
type Output = i32;
fn run() -> Result<i32, std::io::Error> {
Ok(1)
}
}
impl First {
fn new() -> First {
First {}
}
}
struct Second;
impl ValidatedCommand for Second {
type Output = String;
fn run() -> Result<String, std::io::Error> {
Ok(String::from("hello"))
}
}
impl Second {
fn new() -> Second {
Second {}
}
}
Both structs implement the trait, one returning a String and the other an i32.
I'm trying to create a Vec of that trait, but I'm not sure how to go about it. I tried the following:
fn main() {
let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
playground.
which errors with
error[E0191]: the value of the associated type `Output` (from the trait `ValidatedCommand`) must be specified
--> src/main.rs:33:23
|
2 | type Output;
| ------------ `Output` defined here
...
33 | let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
| ^^^^^^^^^^^^^^^^^^^^ associated type `Output` must be specified
error[E0277]: the size for values of type `dyn ValidatedCommand` cannot be known at compilation time
--> src/main.rs:33:19
|
33 | let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
| ^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `std::marker::Sized` is not implemented for `dyn ValidatedCommand`
= note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
= note: required by `std::vec::Vec`
error[E0038]: the trait `ValidatedCommand` cannot be made into an object
--> src/main.rs:33:19
|
33 | let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
| ^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `ValidatedCommand` cannot be made into an object
|
= note: method `run` has no receiver
error[E0308]: mismatched types
--> src/main.rs:33:52
|
33 | let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
| ^^^^^^^^^^^^ expected trait ValidatedCommand, found struct `First`
|
= note: expected type `dyn ValidatedCommand`
found type `First`
error[E0277]: the size for values of type `dyn ValidatedCommand` cannot be known at compilation time
--> src/main.rs:33:47
|
33 | let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `std::marker::Sized` is not implemented for `dyn ValidatedCommand`
= note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
= note: required by `std::slice::<impl [T]>::into_vec`
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error[E0277]: the size for values of type `dyn ValidatedCommand` cannot be known at compilation time
--> src/main.rs:33:47
|
33 | let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `std::marker::Sized` is not implemented for `dyn ValidatedCommand`
= note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
= note: slice and array elements must have `Sized` type
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error[E0038]: the trait `ValidatedCommand` cannot be made into an object
--> src/main.rs:33:47
|
33 | let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `ValidatedCommand` cannot be made into an object
|
= note: method `run` has no receiver
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error[E0277]: the size for values of type `dyn ValidatedCommand` cannot be known at compilation time
--> src/main.rs:33:47
|
33 | let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ doesn't have a size known at compile-time
|
= help: the trait `std::marker::Sized` is not implemented for `dyn ValidatedCommand`
= note: to learn more, visit <https://doc.rust-lang.org/book/second-edition/ch19-04-advanced-types.html#dynamically-sized-types-and-the-sized-trait>
= note: required by `std::vec::Vec`
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
error[E0038]: the trait `ValidatedCommand` cannot be made into an object
--> src/main.rs:33:47
|
33 | let commands: Vec<dyn ValidatedCommand> = vec![First::new(), Second::new()];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `ValidatedCommand` cannot be made into an object
|
= note: method `run` has no receiver
= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
I am thinking that maybe there is a way to make use of the associated type, but I have no idea how I might go about it.
Is there a way to get this vector creation to compile?