Collect into owned vec of owned strings in rust

Question

I am trying to collect into an vec of strings in rust using the following:

let fields : ~[~str] = row.split_str(",").collect();

I get the following error: expected std::iter::FromIterator<&str>, but found std::iter::FromIterator<~str> (str storage differs: expected & but found ~)

I have tried to use type hints but with no success

Answer 1

.split_str returns an iterator over &str slices, that is, it is returning subviews of the row data. The borrowed &str is not an owned ~str: to make this work, either collect to a ~[&str], or, copy each &str into a ~str before collecting:

let first: ~[&str] = row.split_str(",").collect();
let second: ~[~str] = row.split_str(",").map(|s| s.to_owned()).collect();

---

FWIW, if you're splitting on a single-character predicate, then split will be more efficient, (e.g. row.split(',') in this case).

Also, I recommend you upgrade to a more recent version of Rust, 0.11 was recently released, but the nightlies are the recommended install targets (change the 0.10 to 0.11 or master in the above documentation links for the corresponding docs).

With the nightly, the two snippets above would be written as:

let first: Vec<&str> = row.split(',').collect();
let second: Vec<String> = row.split(',').map(|s| s.to_string()).collect();

(Lastly, if you're struggling with the distinction of &str vs. ~str aka String, I wrote up some details a while ago.)