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Forgive me for asking instead of looking, I'm still getting into rust; why do you map instead of getting the result? path.extension().map(|ext| ext == "bun

Forgive me for asking instead of looking, I'm still getting into rust; why do you map instead of getting the result? path.extension().map(|ext| ext == "bundle").unwrap_or(false) vs (path.extension() == "bundle").unwrap_or(false) or further up .map(|e| e.map(|e| e.path())) vs .map(|e| e.path()) Is the .map keeping any value wrapped in an iterator so you can map again? I thought it was interesting what you wrote looks a lot like what I'd write in powershell.

steveklabnik 4y ago
Not your parent, but I do know the answer. extension() returns an Option<&OsStr>, because not every file has an extension https://doc.rust-lang.org/stable/std/path/struct.Path.html#method.extension https://doc.rust-lang.org/stable/std/path/struct.Path.html#m... map on option says "run this closure on the value if it's Some, or do nothing if it's None https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.map https://doc.rust-lang.org/stable/std/option/enum.Option.html... So after the map, we now have an Option<bool>. The unwrap_or method will say "give me the value if it's Some, and give me the argument if it's not https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.unwrap_or https://doc.rust-lang.org/stable/std/option/enum.Option.html... That means we finally end up with a bool. (path.extension() == "bundle").unwrap_or(false) This code wouldn't work because you're comparing an Option<&OsStr> to a &str. Even if that worked, you'd have a boolean, and unwrap_or doesn't make sense on booleans, you'd just leave off that part.
- Already__Taken 4y ago
  Awesome thanks, I wasn't on a machine to play around with it at the time.
0x457 4y ago
`extension()` gives you an `Option`, remember `Path` might not be a file or file could be without extension. Why not `((path.extension() == Some("bundle"))`? I don't know, it didn't work, and I didn't want to spend too much time on it. `read_dir` gives us an iterator over `Result<DirEntry>`, so `e` in that map is a `Result` and not a `DirEntry`. It's two different "map" functions - on Option<T> and Result<T,E> it maps "T", but on Iterator it maps "Item" from that iterator. Here is an explanation why `read_dir` give you a Result - https://doc.rust-lang.org/std/fs/fn.read_dir.html#errors https://doc.rust-lang.org/std/fs/fn.read_dir.html#errors
- Already__Taken 4y ago
  Thanks for the insight

steveklabnik 4y ago

Not your parent, but I do know the answer. extension() returns an Option<&OsStr>, because not every file has an extension https://doc.rust-lang.org/stable/std/path/struct.Path.html#method.extension https://doc.rust-lang.org/stable/std/path/struct.Path.html#m... map on option says "run this closure on the value if it's Some, or do nothing if it's None https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.map https://doc.rust-lang.org/stable/std/option/enum.Option.html... So after the map, we now have an Option<bool>. The unwrap_or method will say "give me the value if it's Some, and give me the argument if it's not https://doc.rust-lang.org/stable/std/option/enum.Option.html#method.unwrap_or https://doc.rust-lang.org/stable/std/option/enum.Option.html... That means we finally end up with a bool. (path.extension() == "bundle").unwrap_or(false) This code wouldn't work because you're comparing an Option<&OsStr> to a &str. Even if that worked, you'd have a boolean, and unwrap_or doesn't make sense on booleans, you'd just leave off that part.

Already__Taken 4y ago
Awesome thanks, I wasn't on a machine to play around with it at the time.

0x457 4y ago

`extension()` gives you an `Option`, remember `Path` might not be a file or file could be without extension. Why not `((path.extension() == Some("bundle"))`? I don't know, it didn't work, and I didn't want to spend too much time on it. `read_dir` gives us an iterator over `Result<DirEntry>`, so `e` in that map is a `Result` and not a `DirEntry`. It's two different "map" functions - on Option<T> and Result<T,E> it maps "T", but on Iterator it maps "Item" from that iterator. Here is an explanation why `read_dir` give you a Result - https://doc.rust-lang.org/std/fs/fn.read_dir.html#errors https://doc.rust-lang.org/std/fs/fn.read_dir.html#errors

Already__Taken 4y ago
Thanks for the insight