Convert Vec into a slice of &str in Rust?

Question

Per Steve Klabnik\'s writeup in the pre-Rust 1.0 documentation on the difference between String and &str, in Rust you should use &str unless you really

Answer 1

This is actually impossible without memory allocation¹.

Going from String to &str is not just viewing the bits in a different light; String and &str have a different memory layout, and thus going from one to the other requires creating a new object. The same applies to Vec and &[]

Therefore, whilst you can go from Vec to &[T], and thus from Vec to &[String], you cannot directly go from Vec to &[&str]. Your choices are:

• either accept &[String]
• allocate a new Vec<&str> referencing the first Vec, and convert that into a &[&str]

As an example of the allocation:

fn usage(_: &[&str]) {}

fn main() {
    let owned = vec![String::new()];

    let half_owned: Vec<_> = owned.iter().map(String::as_str).collect();

    usage(&half_owned);
}

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¹ The conversion required is impossible, however using generics and the AsRef bound as shown in @aSpex's answer you get a slightly more verbose function declaration with the flexibility you were asking for.