How do I get a &str or String from std::borrow::Cow<str>?

Question

I have a Cow:

use std::borrow::Cow;  // Cow = clone on write
let example = Cow::from("def")

I would like to get the def back out of it, in order to append it to another String:

let mut alphabet: String = "ab".to_string();
alphabet.push_str("c");
// here I would like to do:
alphabet.push_str(example);

This does not work and I don't see the appropriate method in Cow to get the &str or String back out.

Answer 1

How do I get a &str

1. Use Borrow:

   use std::borrow::Borrow; alphabet.push_str(example.borrow()); 

2. Use AsRef:

   alphabet.push_str(example.as_ref()); 

3. Use Deref explicitly:

   use std::ops::Deref; alphabet.push_str(example.deref()); 

4. Use Deref implicitly through a coercion:

   alphabet.push_str(&example); 

How do I get a String

1. Use ToString:

   example.to_string(); 

2. Use Cow::into_owned:

   example.into_owned(); 

3. Use any method to get a reference and then call to_owned:

   example.as_ref().to_owned(); 

Answer 2

Pass a reference to example (i.e. &example) to push_str.

let mut alphabet: String = "ab".to_string();
alphabet.push_str("c");  
alphabet.push_str(&example);

This works because Cow implements Deref.