Update of Contract information

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

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

Thanks for the explanation.

3 posts were split to a new topic: Last statement in a do block must be an expression?

4 posts were split to a new topic: Couldn’t match type ‘Update’ with ‘(->) c0’

3 posts were split to a new topic: Conflicting definitions for ‘alias’