How to return a String created in the code?

[szabgab]

While experimenting with Rocket I tried to send back a generated string.

#[macro_use]
extern crate rocket;

#[get("/")]
fn index() -> &'static str {
    let answer = 42;
    format!("The answer is {}", answer)
    //format!("The answer is {}", answer).as_str()
}

#[launch]
fn rocket() -> _ {
    rocket::build().mount("/", routes![index])
}

I got an error:

expected `&str`, found `String`

I tried to call as_str() and then I got

returns a value referencing data owned by the current function

I could use a Template, but I wonder if there is a way to send back a string.

I could also define the return to be String and then this would work, but the in examples I saw on the Rocket site the examples return &str. Does returning String have issues?

#[macro_use]
extern crate rocket;

#[get("/")]
fn index() -> String {
    let count = 42;
    format!("The answer is {}", count)
}

#[launch]
fn rocket() -> _ {
    rocket::build().mount("/", routes![index])
}

[SergioBenitez]

No, that's perfectly correct. You cannot return a reference to something that heap allocated on the outgoing frame; that would be a dangling pointer.