How to initialize a discriminated union from another discriminated union in F#? - f#

Question

With the following F# definitions, how can the Model be initialized?
open System
open System.Windows
type ContactDetail = { Id: Guid; Name: string; Content: string; Text: string }
type Internet = { Id: Guid; Name: string; Content: string; Text: string }
type PhoneNumber = { Id: Guid; Name: string; Content: string; Text: string }
type Address = { Id: Guid; Name: string; Content: string; Text: string }
module Testing =
type Details =
| ContactDetail of ContactDetail
| Internet of Internet
| PhoneNumber of PhoneNumber
| Address of Address
let contactDetail : ContactDetail = {Id=Guid.NewGuid(); Name="Contact Detail"; Content="Content for Contact Detail"; Text="here is the contact detail text" }
let internet : Internet = {Id=Guid.NewGuid(); Name="Internet"; Content="Content for Internet"; Text="here is the internet text" }
let phoneNumber : PhoneNumber = {Id=Guid.NewGuid();Name="Phone Number"; Content="Content for phone number"; Text="here is the phone number text" }
let address : Address = {Id=Guid.NewGuid(); Name="Address"; Content="Content for Address"; Text="here is the Address text" }
let details = [ContactDetail contactDetail
Internet internet
PhoneNumber phoneNumber
Address address
]
type DetailsWithId = DetailsWithId of Details * Guid
type Model = {
ClickCount: int
Message: string
Details: DetailsWithId list
}
More specifically, I need Details of the Model to be a list (or seq). Is type DetailsWithId already a list because of type Details?
TIA

Answer 1

As explained in the comment, a value of your Details type represents just a single detail - one of the several possible details listed. A value of type Details list is a list of details (which can possibly be empty, or it can include multiple instances of the same detail type).
If this is not what you need, then it'd be good to find a model that better captures the structure of your domain.
If this is what you want, then I would still change two things about your data types:
First, I'd rethink how you're storing IDs. In your model, you have Id field in the individual records, but then, again, in the DetailsWithId type. I suppose the question is how to automatically copy the ID from the record to the ID in the DetailsWithId type. There is no easy way to do this, but it's better to design your types so that you do not need to do this.
Second, your four record types i.e. ContactDetail, Internet, etc. are all the same. Wouldn't it be easier to use just one type?
I think working with your data would be a lot easier (unless there is something about your domain that you did not document in the question), if you used a type definition like this:
type DetailKind =
| ContactDetail
| Internet
| PhoneNumber
| Address
type Detail =
{ Id: Guid
Name: string
Content: string
Text: string
Kind: DetailKind }
type Details = Detail list