I want to update an A cdt with another B cdt which is subset of A cdt. Is there

Do the field attributes have the same name? If so you can just save the PV into the subset PV, Appian will map the values by attribute name

You can use a script task to do that , you just have to map the values from B cdt to A cdt in the output expression. Rest Appian will take care.

You can create a expression rule and pass cdtA and cdtB into it. Use type!cdtA() and map the cdtA fields with cdtB fields.
Ex:
type!cdtA(
id: if(APP_isnull(ri!cdtB.id),ri!cdtA.id,ri!cdtB.id)
name: if(APP_isnull(ri!cdtB.name),ri!cdtA.name,ri!cdtB.name)
gender: if(APP_isnull(ri!cdtB.gender),ri!cdtA.gender,ri!cdtB.gender)
age: ri!cdtA.age /* If age field is present only in cdtA and not in cdtB */
)

This way you can update the cdtA efficiently preserving the non-common fields also.

Lets me know if the information was helpful.

You can also use updatecdt function to update specific fields. Say if you have 10 field in your cdt and you want to update only one field (which is also a cdt as in your case), then try something like

updatecdt(
ri!parentCDT,
{
childCDT: rule!returnModifiedChildValues(ri!parentCDT.childCDT)
}
)

Here rest of the 9 field values will be preserved.

@kumaraveln - Correct me if I am wrong updatecdt is not OOTB i.e its a shared component and it is compatible till Appian 7.6 version. Please share some light on the expression rule returnModifiedChildValues().

Hi Shaoyongw,

Create a expression rule with two rule inputs of type (AnyType) and pass your A CDT and B CDT

Define in fn!type that to which CDT you want to update.. Follow the code like below it will do what actually you want to do in a Expression Rule

'type!{urn:xxxx:xxxxxx}<CDT_NAME>'(

name:ri!ACDT.name,
age:ri!BCDT.age,
address:ri!ACDT.address,
workStream:ri!BCDT.workStream
)

@sidhantb: Yes., its not OOTB but we are still using it in 16.1 without any issue. I did not understand the use case here completely so just thought of sharing an option to easily update CDTs. When we use updatecdt() we don't need to do any type casting and no need to mention all the fields as we do for updatearray() or normal variable to variable mapping.

It will be useful when we update very few fields among a large CDT.

And rule!returnModifiedChildValues here is just to do any data manipulation they want to do with the child cdt values. Like updating a lastModifiedDate field inside the child.

@shaoyongw: If you could paste the screenshot of your CDTs here, we could get a clear picture of what you are trying to achieve.

Guyz it's just an small requirement
.. if we do type cast in Expression rule or by mapping in case of process modelling will do the job .... whatever user wants for his own requirement ...

Chill .... !!!!!!!!

Thank you all for your response! At last, I use @sidhantb's way to update the cdt.