Metaprogramming: Map struct to new struct with all fields as Options

I have a struct, and I would like to automatically generate another struct, where all the fields are Options instead of their type from the first struct. I need this to message an update of a database entry, where all unchanged fields are None and all fields to be updated should be Some(T).
Can I do this in Rust? I would like the definition of the update struct to automatically adapt to changes in the real struct.

You can do this with a macro. There are some examples of macros that loop over all fields of a struct, notably serde_derive.

Something like this?

opt_struct! {
    #[derive(Default, Debug)]
    struct Foo[T] {
        foo: T,
    } => OptionFoo
  • Playground

  • For more powerful and with nicer ergonomics metaprogramming, you can use procedural macros.


Thank you everyone! I will have to dig into this properly.. especially procedural macros. This is a great video by Jon Gjengset, for anyone interested.