TLDR;
I did not find an easy way to clean up NSArray, but there is a better option to get NSString from pasteboard - stringForType.

Next up. Even if send release to NSString, there are leftovers after conversion NSString to Rust string. Right now, conversion happens in INSString.as_str(), which internally uses NSString.UTF8String. UTF8String, according to Apple docs, is a pointer lifetime of which is less or equal NSString. This is not true if the clipboard contains characters outside the ASCII range. That's why nsstring_to_rust_string function.

I tried to describe the full process here https://barhamon.com/post/rust_and_nsstring

This should be done at rust_objc_fondation.
Updating original pull request, just in case it need to be fixed right now

Since we get our string from pasteboard, we need to inform objc runtime that we finished using it. We can do it by ourselves by sending the release message or use Id::from_retained_ptr, and Id will release that NSString when it goes out of scope.