Get array slice of str from vector of objects containing str-CodePudding

I have a vector of objects/instances (not sure what the rust parlance is) which have a field containing a string slice. I need to create an array slice containing the string slice fields. Below is my attempt. I am trying to get foo_bars to be the same as what_i_want.

struct Foo<'a> {
    bar: &'a str,
}
let foos = vec![Foo { bar: "one" }, Foo { bar: "two" }, Foo { bar: "three" }];
let foo_bars: Vec<str> = foos.into_iter().map(|foo| foo.bar).collect();

let what_i_want = &["one", "two", "three"];

CodePudding user response：

You're missing the & in Vec<&str>.

Here's a playground that works.

struct Foo<'a> {
    bar: &'a str,
}

fn main() {
    let foos = vec![Foo { bar: "one" }, Foo { bar: "two" }, Foo { bar: "three" }];
    let foo_bars: Vec<&str> = foos.into_iter().map(|foo| foo.bar).collect();

    let what_i_want = &["one", "two", "three"];

    println!("{:?}", foo_bars == what_i_want);
}

CodePudding user response：

Everything must have fixed size, str mean a range of characters in string, And the size of string slice can be very.

You need to use a pointer &. A pointer is fixed size (usize). Depend on cpu architecture (32 or 64) bits.

let foo_bars: Vec< str> = foos.into_iter().map(|foo| foo.bar).collect();
                  ^ add a `&` here