Property validation

[kkmann]

Dear all,

I was wondering whether it would be feasible to add optional constraints to property definitions like

myclass <- new_class("myclass", properties = list(
  a = class_double(min = 0, na_ok = FALSE)
))

Ideally, this would then also be picked up by roxygen2 when documenting class properites. Might be out of scope of a OOP system, but would be kind of handy to have...

Alternatively, do you see a way of standardizing input checking like this in the validator to autogenerate documentation of the constraints?

[lawremi]

There could be convenience functions for constructing properties with constraints like this. There's precedent for this sort of thing in property implementations from other languages.

[hadley]

We'd also need to add the idea of a property validator, but I think that makes sense.

Would be worth considering whether we want to provide canned property classes that represent scalars (but that's a fairly big design problem, so might be worth leaving that to a package).

[jl5000]

In my own use of S7 I would certainly find this very useful. I have implemented a set of validator functions dependent on the type of property:

• Min/max length of atomic vectors/lists
• Min/max character length of strings
• Min/max values of numerics
• Ensuring character properties fit regex patterns
• Ensuring character properties take one of a number of set values
• Ensuring lists contain elements of acceptable classes

Incorporating any of these into S7 would be useful.