toRepresentation/fromRepresentation for a single field?

[timotheecour]

@s-ludwig
Can we define a toRepresentation/fromRepresentation for a single field?
eg if I have a single (or a few) problematic field but the other ones should follow the default serialization/deserialization rules

ideally it'd work as an UDA:

struct Foo{
 int normal1;
 string normal2;
 string fun1(){...}
 auto fun2(string repr){...}
 @toRepresentationCustom!fun1
 @fromRepresentationCustom!fun2
 byte[]bar;
}

[s-ludwig]

A way to achieve this without UDA support is to use properties:

struct Foo {
    @ignore byte[] bar;
    @property @name("bar") {
        string barString() const { return ...; }
        void barString(string) { bar = ...; }
    }
}

toRepresentation would require a custom type, similar to this:

struct Bar {
    byte[] data;
    alias data this;
    string toRepresentation() { ... }
    static void fromRepresentation() {}
}

struct Foo {
    Bar bar;
}

[timotheecour]

@s-ludwig Thanks!

• how about if we want to override to/from Bson conversion (instead of to/from string), eg to map DateTime to Bson's DateTime (but more generally than that example)?
• what if I have little control over Foo (eg it is auto generated such as via dproto), how would define barString outside of Foo (again, in the single field case) ?

Sorry for the noob questions ...

[timotheecour]

ping on this, especially the 2nd point: what if I have little control over Foo (eg generated via dproto)