Domain Modeling Made Functional

Putting It All Together

We’ve created a lot of types in the chapter, so let’s step back and look at how they fit together as a whole, as a complete domain model.

First, we put all these types in a namespace called OrderTaking.Domain, which is used to keep these types separate from other namespaces. In other words, we’re using a namespace in F# to indicate a DDD bounded context, at least for now.

namespace OrderTaking.Domain

// types follow

Then let’s add the simple types.

// Product code related
type WidgetCode = WidgetCode of string
  // constraint: starting with "W" then 4 digits
type GizmoCode = GizmoCode of string
  // constraint: starting with "G" then 3 digits
type ProductCode =
  | Widget of WidgetCode ...