since: my first project

Ephera, 21 days ago (edited 14 days ago)

I took a very quick look at the code and one thing I noticed, is that you’re using &String.

For a parameter in a function, you always want to use &str instead, as explained here: doc.rust-lang.org/book/ch04-03-slices.html#string…

I believe, it’s also not a thing to return &String (nor to store it in a struct). I don’t have as solid of an explanation for it, it’s just not something I see much in Rust code (and in the chapter above, they do use a &str as return value, too).
Maybe someone else can weigh in on that.

The same applies for:

• &[] rather than &Vec
• &Path rather than &PathBuf
• &OsStr rather than &OsString

I would also recommend using Clippy. I think, you can just run cargo clippy and it’ll work.
It’s a linter and will tell you lots of code style issues (like using &String as a parameter).
If you’ve never run it, it might spit out a lot of warnings at first, but working through them can teach you quite some things.

ExperimentalGuy, 21 days ago

Thanks, that was a lot of info I didn’t know either. I was wondering how to use clippy…

larix, 21 days ago (edited 14 days ago)

Thank you very much. I’ll change it. I did run cargo clippy, but it didn’t complained anything anymore before I published the code. 🙂

One question to return value Option<&String>:

is it better to change to Option<&str> or &Option<String> if the value in the struct is a Option<String>? The latter sounds more logical to me.

Ephera, 20 days ago

Hmm, not quite sure why Clippy didn’t say anything then. I think, it was a Option<&String> which I had seen as a parameter type. Maybe it doesn’t complain when it’s wrapped in an Option…

jcbritobr, 21 days ago

@larix @Ephera it's better to return an Option<&str> as a String may DeRef to &str.

For example

self.name.as_deref()

Ephera, 20 days ago

Hmm, interesting. The documentation tells me, it creates a new Option value, and allocating memory every time someone just wants to look at a value could be pretty bad.

But I guess, an Option of a reference never needs to allocate memory, because it’ll either be a pointer to a value (Some) or a pointer to null (None). Right?

Well, that explains why it’s technically possible.
As for why Option<&str> is preferrable then:
It hides away your internals. Your caller should only care whether they can get the value or not (Some vs. None), not what the precise reason is. That reason or your internal structure might change.

@larix

larix, 20 days ago

Well, that explains why it’s technically possible.

As for why Option<&str> is preferrable then: It hides away your internals. Your caller should only care whether they can get the value or not (Some vs. None), not what the precise reason is. That reason or your internal structure might change.

Yes, that makes sense too. Great!

I’ve updated the code as recommended.

@Ephera@jcbritobr@mastodon.social

maiskanzler, 21 days ago

Very neat idea!

larix, 21 days ago

Thanks!