Manipulating record in template - daml

Question

I'd like to make some structure over the code and introduce records in the template. With the simple version it works fine, though with records not working. Can you advise?
Thanks
-- WORKING VERSION --
daml 1.2
module Magic_potion where
template Potion_Taken
with
holder : Party
tube_id : Text
where
signatory holder
controller holder can
UpdateData : ContractId Potion_Taken
with
newTube_id : Text
do
create this with
tube_id = newTube_id
sampling_1 = scenario do
w <- getParty "Wizard 1"
potionTaken <- submit w do create Potion_Taken with holder = w; tube_id = "tube 1"
newPotionTaken <- submit w do exercise potionTaken UpdateData with newTube_id = "tube 2"
submit w do
newP <- fetch newPotionTaken
assert (newP.tube_id == "tube 2")
-- FAULTY VERSION --
data Content = Content
with
tube_id : Text
template Potion_Taken
with
holder : Party
content : Content
where
signatory holder
controller holder can
UpdateData : ContractId Potion_Taken
with
newTube_id : Text
do
create this with
content.tube_id = newTube_id -- This line seems to be the trouble
sampling_1 = scenario do
w <- getParty "Wizard 1"
potionTaken <- submit w do create Potion_Taken with holder = h; content = Content with tube_id = "tube 1"
newPotionTaken <- submit h do exercise potionTaken UpdateData with newTube_id = "tube 2"
submit w do
newB <- fetch newPotionTaken
assert (newP.content.tube_id == "tube 2")

Answer 1

create this with
content.tube_id = newTube_id -- This line seems to be the trouble
This is indeed your problem. To avoid ambiguity, the with clause only allows a single level of naming. What this means is that if you want a new Content record in your Potion_Taken record, you will need to create one. Fortunately with nests cleanly so it isn't too cumbersome.
create this with
content = Content with tube_id = newTube_id
Moreover, if Content has multiple fields and you only want to update a subset, the copy-constructor syntax also works here:
create this with
content = this.content with tube_id = newTube_id