RDB から選択型を読み取る

実例

code:fsharp

type Contact =

{ ContactId: ContactId

Info: ContactInfo }

and ContactInfo =

| Email of EmailAddress

| Phone of PhoneNumber

and EmailAddress = EmailAddress of string

and PhoneNumber = PhoneNumber of string

and ContactId = ContactId of int

1. クエリの型を定義する

code:fsharp

type ReadOneContact = SqlCommandProvider<"""

SELECT ContactId, IsEmail, IsPhone, EmailAddress, PhoneNumber

FROM ContactInfo

WHERE ContactId = @contactId

""", connectionString>

code:fsharp

let toDomain (dbRecord: ReadOneContact.Record): Result<Contact,_> =

result {

let! contactId =

dbRecord.ContactId

|> ContactId.create

let! contactInfo =

if dbRecord.IsEmail then

result {

let! emailAddressString =

dbRecord.EmailAddress

|> Result.ofOption "Email expected to be non null"

let! emailAddress =

emailAddressString |> EmailAddress.create

return (Email emailAddress)

}

else

result {

let! phoneNumberString =

dbRecord.PhoneNumber

|> Result.ofOption "PhoneNumber expected to be non null"

let! phoneNumber =

phoneNumberString |> PhoneNumber.create

return (Phone phoneNumber)

}

let contact =

{ ContactId = contactId

Info = contactInfo }

return contact

}

code:fsharp

module Result =

let ofOption errorValue opt =

match opt with

| Some v -> Ok v

| None -> Error errorValue

code:fsharp

let readOneContact (productionConnection: SqlConnection) (ContactId contactId) =

use cmd = new ReadOneContact(productionConnection)

let tableName = "ContactInfo"

let records = cmd.Execute(contactId = contactId) |> Seq.toList

convertSingleDbRecord tableName contactId records toDomain