Update of Contract information

[bartcant]

I am experimenting with DAML and wanted to write a module that saves and updates the details of a “Citizen” called CitizenInfo. I also added a Key = CitizenKey

I have the following DAML code

module Registration where
data CitizenInfo = CitizenInfo with
  citizendetail1 : Text
  citizendetail2 : Text
  citizendetail3 : Text
   deriving (Eq, Show)

data CitizenKey = CitizenKey with
  citizen : Party
  id : Text
   deriving (Eq, Show)

template CitizenRegistration
 with
     registrationCid : CitizenKey
     registrationData : CitizenInfo

  where
     signatory registrationCid.citizen
     key registrationCid : CitizenKey
     maintainer key.citizen
     controller registrationCid.citizen can 
       nonconsuming Register : ContractId CitizenRegistration with
          newRegistrationCid : CitizenKey
          newRegistrationData : CitizenInfo
        do
         create CitizenRegistration with
            registrationCid = newRegistrationCid
            registrationData = newRegistrationData

       nonconsuming UpdateRegistration : ContractId CitizenRegistration
         with
           newCitizenDetails : CitizenInfo
        do
         (oldRegistrationCid, oldRegistrationData) <- fetchByKey @CitizenRegistration (key this)
         archive oldRegistrationCid
         create CitizenRegistration with 
           registrationCid = oldRegistrationCid  
           registrationData = newCitizenDetails

It currently gives me the following error message at the 2nd last line

 Couldn't match expected type ‘CitizenKey’
                  with actual type ‘ContractId CitizenRegistration’
    • In the ‘registrationCid’ field of a record
      In the first argument of ‘create’, namely
        ‘CitizenRegistration
           {registrationCid = oldRegistrationCid,
            registrationData = newCitizenDetails}’
      In a stmt of a 'do' block:
        create
          CitizenRegistration
            {registrationCid = oldRegistrationCid,
             registrationData = newCitizenDetails}type

Also I want to write a scenario for the UpdateRegistration, so any insights are welcome

[cocreature]

You are mixing up contract ids and the data associated with the contract with the given id. registrationCid does not in fact store a contract id. It stores a contract key. So you also need to pass in the contract key not the contract id. Given the data of a template (here oldRegistrationData) you can always use the key function to get the contract key, So to fix your example you can use

create CitizenRegistration with 
           registrationCid = key oldRegistrationData
           registrationData = newCitizenDetails

[bartcant]

Thanks for the explanation.