F x=1:1:$L(customString,",")  dosomething($P(customString,",",x))

1. Hi.

Maybe you should use calculated property - something like this:

Class User.CExampleJSON Extends (%RegisteredObject, %JSON.Adaptor, %XML.Adaptor)
{
Property something As %Integer(%JSONINCLUDE = "NONE", DISPLAYLIST = ",OK,Error,Warning", VALUELIST = ",0,1,2") [ InitialExpression = 0 ];

ClassMethod RunMe()
{
      set obj = ..%New()
      set obj.something = 2       
      do obj.%JSONExportToString(.string)
      write "JSON : " _ string,!!!
      write "Content : " _ ..somethingLogicalToDisplay(obj.something),!
}

Property somethingDisplay As %String(%JSONFIELDNAME = "something") [ Calculated ]; Method somethingDisplayGet() As %String [ ServerOnly = 1 ]
{
Quit ..somethingLogicalToDisplay(..something)
}

}

I'm trying to pass JSON serialized parameter to native .NET API method ClassMethodIRISList, but Stream type is not possible.