%JSON.Adaptor with class that inherit from %ListOfObjects

Discussion

Javier Llobet · Jul 8, 2020

I was trying the %JSON.Adapter backport to cache and try it also in IRIS and i found a kind of an issue regarding to export and object to json that is an inheritance of %ListOfObjects
If we have a list of elementtype of and object and then we try to export this to a json we get this json instead of a correct json.

exported json:

{
"ElementType":"test.element",
"Size":"1"
}

Json that we want:

[
  {
    "field1":"testField1",
    "field2":"testField2"
  }
]

Test classes:

Class test.elementList Extends (%ListOfObjects, %ZJSON.Adaptor)
{ 
 /// The type (class name) of the elements stored in the collection.
 Parameter ELEMENTTYPE = "test.element";
}

Class test.element Extends (%RegisteredObject, %ZJSON.Adaptor)
{ 
 Property field1 As %String [ InitialExpression = "testField1" ];
 Property field2 As %String [ InitialExpression = "testField2" ];
}

Class test.Main Extends %RegisteredObject
{ 
ClassMethod Run()
{
  Set elem = ##class(test.element).%New()
  Set elemList = ##class(test.elementList).%New()
  Do elemList.Insert(elem)
  Do elemList.%JSONExportToString(.json)
  Do ##class(%ZJSON.Formatter).%New().Format(json)
 } 
}

I could fix it overwritting the %JSONExportToString in the elementList class in order to loop over elements and so on...but can be possible to fix this in IRIS? or is there any other solution?

Thanks !

Class test.elementList Extends (%ListOfObjects, %JSON.Adaptor) { /// The type (class name) of the elements stored in the collection. Parameter ELEMENTTYPE = "test.element"; /// Returns this object as a JSON Stream Method %JSONExportToStream(ByRef objStream As %Stream.Object, %mappingName As %String = "") As %Status { #Dim objStream As %Stream.TmpCharacter = ##class(%Stream.TmpCharacter).%New() Do objStream.Write("[") For i=1:1:..Size { Do ..GetAt(i).%JSONExportToStream(.objStream, %mappingName) If (i<..Size) { Do objStream.Write(",") } } Do objStream.Write("]") Return $$$OK } /// Returns this object as a JSON string Method %JSONExportToString(ByRef jsn As %String, %mappingName As %String = "") As %Status { #Dim jsonElement As %String = "" Set jsn = "[" For i=1:1:..Size { Set jsonElement = "" Do ..GetAt(i).%JSONExportToString(.jsonElement, %mappingName) Set jsn = jsn_jsonElement If (i<..Size) { Set jsn = jsn_"," } } Set jsn = jsn_"]" Return $$$OK } }

Robert Cemper · Jul 8, 2020

Just to verify if this is a %JSON specific problem I added also %XML.Adaptor to the classes.
And there is a similar problem: %ListOfObjects seems to be the bad guy.

Do elemList.%JSONExport() {"ElementType":"Test.element","Size":1} Do elemList.XMLExport() <elementList><ElementType>Test.element</ElementType><Size>1</Size></elementList> zw elemList elemList=2@Test.elementList ; <OREF> +----------------- general information --------------- | oref value: 2 | class name: Test.elementList | reference count: 2 +----------------- attribute values ------------------ | Data(1) = "" | ElementType = "Test.element" | Oref(1) = "1@Test.element" | Size = 1 <Set> +-----------------------------------------------------

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With a small extension, you may get closer to your result.
What you expect is a JSON Array, but %JSONExport... works on data OBJECTS, not on data TYPES { same as XMLExport() }

So I have created a small wrapper object:

Class Test.javier Extends (%RegisteredObject, %JSON.Adaptor) 
{ Property wrap As Test.elementList(%JSONFIELDNAME = " "); }

extending Test.Main:

Class Test.Main Extends %RegisteredObject { ClassMethod Run() { Set elem = ##class(Test.element).%New() Set elemList = ##class(Test.elementList).%New() Do elemList.Insert(elem) #; Do elemList.%JSONExportToString(.json) #; Do ##class(%ZJSON.Formatter).%New().Format(json) #;; extended set jav=##class(Test.javier).%New() set jav.wrap=elemList Do jav.%JSONExportToString(.json)
set json=$e($p(json,":",2,*),1,*-1) ; a little bit dirty Do ##class(%ZJSON.Formatter).%New().Format(json) } }

And here we go:

SAMPLES>do ##class(Test.Main).Run() [ { "field1":"testField1", "field2":"testField2" } ] SAMPLES>

I don't know if i will prefer override the %JSONExportToString and %JSONExportToStream or wrapping but that dirty trick..

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