fn get_links(link_nodes: Select) -> Option<String> {
let mut rel_permalink: Option<String> = for node in link_nodes {
link = String::from(node.value().attr("href")?);
return Some(link);
};
Some(rel_permalink)
}
This is what I’m trying to do, and I’ve been stuck with this code for an hour, I simply don’t know how to put this function togheter… Essentially I would like to take some link_nodes
and just return the link String, but I’m stuck in the use of Option with the ?
operator…
Pheraps trying to write it with match would clear things out(?)
Also I come from JavaScript in which expressions do not have their own scope, meaning I’m having troubles to understand how to get out a variable from a for loop, should I initialize the rel_permalink
variable as the for loop result?
This are the errors i get:
error[E0308]: mismatched types
--> src/main.rs:55:49
|
55 | let mut rel_permalink: Option<String> = for node in link_nodes {
| _________________________________________________^
56 | | link = String::from(node.value().attr("href")?);
57 | |
58 | | return Some(link);
59 | | };
| |_________^ expected `Option<String>`, found `()`
|
= note: expected enum `Option<String>`
found unit type `()`
note: the function expects a value to always be returned, but loops might run zero times
--> src/main.rs:55:49
|
55 | let mut rel_permalink: Option<String> = for node in link_nodes {
| ^^^^^^^^^^^^^^^^^^^^^^ this might have zero elements to iterate on
56 | link = String::from(node.value().attr("href")?);
| - if the loop doesn't execute, this value would never get returned
57 |
58 | return Some(link);
| ----------------- if the loop doesn't execute, this value would never get returned
= help: return a value for the case when the loop has zero elements to iterate on, or consider changing the return type to account for that possibility
You should use filter_map instead of the retain and later unwrapping and you don’t need a fold to build a Vec from an iterator, you can just use collect for that at the end.
here, it definitely is shorter, I’ll keep filter_map in mind, thanks:
fn get_links(mut link_nodes: Select) -> Vec<String> { link_nodes.into_iter().filter_map(|node| node.value().attr("href").map(|href| href.to_string())).collect() }