How to accept &str, String and &String in a single function?

问题

I want to write a single function, that accepts a &str, a String and a borrowed &String. I've written the following 2 functions:

fn accept_str_and_ref_string(value: &str) {
    println!("value: {}", value);
}

fn accept_str_and_string<S: Into<String>>(value: S) {
    let string_value: String = value.into();
    println!("string_value: {}", string_value);
}

fn main() {
    let str_foo = "foo";
    let string_foo = String::from("foo");

    accept_str_and_ref_string(str_foo);
    accept_str_and_ref_string(&string_foo);

    accept_str_and_string(str_foo);
    accept_str_and_string(string_foo);
}

Is it possible to implement one function so that I can do this:

accept_all_strings(str_foo);
accept_all_strings(&string_foo);
accept_all_strings(string_foo);

回答1:

You can use the AsRef<str> trait:

// will accept any object that implements AsRef<str>
fn print<S: AsRef<str>>(stringlike: S) {
    // call as_ref() to get a &str
    let str_ref = stringlike.as_ref();

    println!("got: {:?}", str_ref)
}

fn main() {
    let a: &str = "str";
    let b: String = String::from("String");
    let c: &String = &b;

    print(a);
    print(c);
    print(b);
}

The print function will support any type that implements AsRef<str>, which includes &str, String and &String.

来源：https://stackoverflow.com/questions/55079070/how-to-accept-str-string-and-string-in-a-single-function