Question Re: CAP + Typescript: Draft UPDATE is updating readonly f... in Technology Q&A

CAP + Typescript: Draft UPDATE is updating readonly fields -- a bug?

shf — Mon, 28 Oct 2024 17:10:40 GMT

Hello CAP and Typescript experts,

I have defined an draft-enabled entity with additional computed fields as follows:

entity BaseSystemTypes : managed { @title: '{i18n>Paltr_SystemTypes_ID_label}' key ID : types.SystemType; @title: '{i18n>Paltr_Common_Name}' @mandatory techName : types.TechnicalName; @title: '{i18n>Paltr_Common_title}' @mandatory title : types.Title; @title: '{i18n>Paltr_Common_isUsable_label}' isUsable : Boolean default true; myComputedField: String = (''); }

Within the service SystemTypes as projection on BaseSystemTypes, I let calculate the field myComputedField after READ:

srv.after('READ', SystemTypes, async (req) => { if (!req) return; ... req.forEach((singleEntity: any) => { singleEntity.myComputedField = 'Test'; } }

In the Fiori App, if I create a new draft instance or change one of the fields manually of an existing record, the draft cannot be saved because "Property myComputedField does not exist in myservice.SystemTypes". If I comment the singleEntity.myComputedField = 'Test', the changes on drafts are working.

If I check the database table BaseSystemTypes, I cannot find the calculated field and I can see the calculated field within the draft views and draft table regarding myService_BaseSystemTypes_drafts. This is correct as far as I know.

But getting an error during creation or updating a draft , is this a bug now inside the UI5 framework ? Or do I have to delete now the changes using the srv.on events for CREATE/UPDATE ? I assumed calculated fields are ignored during any updates.

Re: CAP + Typescript: Draft UPDATE is updating readonly fields -- a bug?

catano — Tue, 29 Oct 2024 09:50:33 GMT

Hi,

By the error it seems that the database is not updated for some reason, could you check that somehow?
I just generated the hana artifacts with cds build --for hana for such setup, and the places I see the On-Read calculated fields are: Service.Entity.hdbview, Service.Entity_draft.hdbtable.
Could you share plase how do you check the tables / data?
I tried to edit / save draft of the entity with the On-Read calculated field, and I get no error.

Peter

Re: CAP + Typescript: Draft UPDATE is updating readonly f...

patricebender — Thu, 31 Oct 2024 09:04:54 GMT

In the cds model, a computed field looks like this:'

"foo": { "@Core.Computed": true, "value": { "val": "bar" } }

I'm not sure what you are trying to achieve but if you want to adapt the value of a computed field,
you'd need to manipulate the object properly: `<entity>.foo.value.val = 'YOUR VALUE'`

Re: CAP + Typescript: Draft UPDATE is updating readonly f...

catano — Thu, 31 Oct 2024 13:27:17 GMT

Hi @patricebender , by the setup I think @shf maybe refers to Calculated Elements

Re: CAP + Typescript: Draft UPDATE is updating readonly f...

catano — Thu, 31 Oct 2024 13:29:51 GMT

But I do agree that maybe what it needs to be considered is the use of a Virtual Element.