You can call the Tranform(source,target) class method implemented by classes that extend Ens.DataTransform :

• directly in objectscript code
• through code generated for a BPL or router process ('send' action optionally uses a list of transformation classes that gets applied in sequence to the message before it is sent to target(s)). 
• through code generated by a DTL ('subtransform')

If you need to process the entire file and no line filtering, I would go for using pass through file service (EnsLib.File.PassthroughService) to send an instance of stream container (Ens.StreamContainer) to either a message router (EnsLib.MsgRouter.RoutingEngine) or custom (BPL or code) process, and use a transform (class extending Ens.DataTransform) to transform the source stream container into a target stream container and send it to the file pass through operation (EnsLib.File.PassthroughOperation) for output.

I would use a custom process over message router if transform needs data source(s) (e.g. response from another process or operation) other than the input file. The transform can pick a suitable target stream class (Extending %Stream.Object) to hold in the Ens.StreamContainer depending on where you want to store the data (database vs file system,…)

HTH

Merry Christmas everyone !

My first time with AoC was a lot of fun, thank you for running this Objectscript ladder.

Congratulations to all participants.

My repository: https://github.com/theanor/idc-aoc-2022-theanor

And quality scanner status : https://community.objectscriptquality.com/dashboard?id=intersystems_iris_community%2Fidc-aoc-2022-theanor

To get an IRIS session integrated in VSCode terminal, you can add it to settings.json :

  "terminal.integrated.profiles.windows": {
        "IRIS Terminal": {
            "path": [
                "C:\\InterSystems\\IRISHealth\\bin\\irissession.exe"
            ],
            "args": ["<instance name>"],
            "icon": "terminal-cmd"
        }
    }

However, this terminal window will lack the niceties of the ISC Terminal application, such as command history.

Hi Ben,

You can use EnsLib.HL7.Schema ResolveSchemaTypeToDocType() class method to resolve DocType dynamically.

For example, if message is an OREF to an instance of EnsLib.HL7.Message :

s message.DocType = ##class(EnsLib.HL7.Schema).ResolveSchemaTypeToDocType("2.5",message.Name)