Error

Convert the String to a string slice (&str) using the .as_str() method or add a reference (&) before the variable name.

fn example(input: &str) {
    let my_string = String::from("hello");
    example(my_string.as_str());
}

Alternatively, if you own the String and don't need it afterwards, pass a reference directly:

fn example(input: &str) {
    let my_string = String::from("hello");
    example(&my_string);
}

If you control the function definition and want to accept ownership of the String, change the parameter type to String:

fn example(input: String) {
    // use input
}

The error occurs because &str is a borrowed string slice (a view into a string), while String is an owned, heap-allocated string. Rust does not automatically convert between them to prevent accidental data copying or ownership confusion.

The "expected &str, found String" error happens when you try to give a function a full string (String) when it only wants to look at a piece of text (&str). Think of it like trying to hand someone your entire house (String) when they only asked to borrow a key to peek inside (&str). You fix it by either giving them just the key (a reference) or changing what they asked for.