Return HashMap type from function

GraXx 0
Viewed 53

In the following function, I am creating a new HashMap with entries from a file (divided in name & value -> I am trying to read a meminfo file from Linux). I am stuck on how to return the values of the hashmap. Am I approaching this in the right way or should this be done differently?

fn read_file_to_hashmap(file_name: impl AsRef<Path>) -> HashMap<String, String> {
    let file = BufReader::new(File::open(&file_name).expect("error here"));

    let hash_map = ["name", "value"]
        .into_iter()
        .zip(file.lines().map(Result::unwrap))
        .collect::<HashMap<_, _>>();
    return hash_map;
}

Here is the error I get:

    error[E0308]: mismatched types
--> src/main.rs:15:12
|
8  | fn read_file_to_hashmap(file_name: impl AsRef<Path>) -> HashMap<String, String> {
|                                                         ----------------------- expected `HashMap<std::string::String, std::string::String>` because of return type
...
15 |     return hash_map;
|            ^^^^^^^^ expected struct `std::string::String`, found `&str`
|
= note: expected struct `HashMap<std::string::String, _>`
            found struct `HashMap<&str, _>`
rust-cargo rust
1 Answers

A string literal "foo" is a &'static str. In your case, "name" and "value" has type &str, but you need String. So just convert it to String by using .to_string() on &str.

fn read_file_to_hashmap(file_name: impl AsRef<Path>) -> HashMap<String, String> {
    let file = BufReader::new(File::open(&file_name).expect("error here"));

    let hash_map = ["name".to_string(), "value".to_string()]
        .into_iter()
        .zip(file.lines().map(Result::unwrap))
        .collect::<HashMap<_, _>>();
    return hash_map;
}
Aditya Supugade0
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