Show HN: Mapperly – A .NET source generator for object to object mappings

Re:Show HN: Mapperly – A .NET source generator for object to... by mjburgess on Thursday January 12, 2023 @08:50AM (#34353429)

I assume the automapper is subsetting on the target type's structure, right?

So its something like this,

    target_dto = { k: MyDbModel.get(k) for k in MyTargetModel.keys() }

Writing this is a big issue with simple static languages (ie., those without much compile-time programming).

This deficiency should really be addressed at the language-level. Ie., what you want is structural typing in the view-layer, and a means of restructuring (ie., filtering) the original db object.

So,

    renderView(myDbModel as {Just,The,Necessary,Fields})

I'd imagine with C# Shapes, Extension Methods and Pattern Matching, you'd be able to do roughly this -- but i'm not sure of the status of "shapes" (ie., typeclasses) in the C# RFC process.

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Re:Show HN: Mapperly – A .NET source generator for object to... by orra on Thursday January 12, 2023 @01:13PM (#34357959)

Thanks for this thoughtout reply. Automapping can also be used for renaming, and simple type conversions.

But yes, structural typing and other interesting typesystems can make this first class.

I didn't realise serious work had been put into typeclasses for C#. Interesting, but unfortunately it seems to have stalled.

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