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Abion47 / darq

A port of .NET's LINQ IEnumerable functions to Dart.
MIT License
85 stars 9 forks source link

Missing DateTime comparsion #10

Closed janosroden closed 2 years ago

janosroden commented 3 years ago

@andrewackerman Awesome package, dart standard library missing the lot of stuff from .NET!

I just noticed the orderBy doesn't support DateTime. I looked the code and I saw you picked several 'scalar' types to support. I guess you missed the Comparable type which is implemented by these types (including DateTime) except Iterable.

Of course tryForType and registerEqualityComparer should search slightly different but I think it would worth the effort. Actually EqualityComparer is a little bit unnecessary because Comparable<T> gives interface for both equality check and sorting; Object offers a way to override hashCode. Anybody who wants to change the behaviour just need to wrap that special handled type with custom overrides.

I'm happy to create a PR if you agree with the changes and have time to review/publish.

Abion47 commented 3 years ago

I hadn't considered DateTime, that would be a good addition to the pre-built comparers. The choice to use a custom EqualityComparer rather than to just use Comparable was intentional, though it would be good to have some built-in interop added.

The purpose of using the class-based EqualityComparer rather than the interface-based Comparer is so that equality, hashing, and sorting can be supported even by types that don't implement Comparable, which is particularly important when dealing with a type that the user doesn't have the ability to change the type in order to inherit it (such as a type coming from a third-party package). Another reason is for convenience - if you only need to sort in one place, it is easier to specify 1-3 lambdas rather than implementing Comparable on the type itself.