Theo Stolker · Dec 22, 2022

%DynamicObject: How to insert json property at a specific location?


I know json does not impose any order, but for readability I would like to insert a json property at a specific location at the start of a %DynamicObject, not at the end.
Is there a known way to do that (other than string manipulation)?

Product version: IRIS 2022.1
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/// Python reorder FHIR properties

ClassMethod PyFHIRResourceReOrder(resource As %String) As %String [ Language = python ]


    import json

    from collections import OrderedDict

    result = json.loads(resource, object_pairs_hook=OrderedDict)

    result.move_to_end("extension", last = False)

    result.move_to_end("meta", last = False)

    result.move_to_end("id", last = False)

    result.move_to_end("resourceType", last = False)

    return json.dumps(result)


This Python code is what I ended up with. It re-orders the properties "resourceType", "id", "meta" and "extension" to be at the start

String manipulation under covers!  sad

Yes, although the Python code does deal with an actual collection object :)

If you want to reorder JSON properties (alphabetically or just put some of them at the beginning) then use a utility method, like this, especially if you have several object(types) to reorder

Class DC.Utility Extends %RegisteredObject
/// Reorder a JSON Object or Array
/// obj:  JSON-Object
/// 	  ord: prop1, prop2, ...	Desired order for (some) properties
/// 	       (Properties not listed are copied in the order in which they were created)
/// 	       If ord not present, properties will be reordered in aplphabetical order
/// obj: JSON-Array
/// 	 ord: pos1, pos2, ...	Desired order for (some) array items
/// 	      (Items not listed are copied in ascending order)
ClassMethod ReOrder(obj As %DynamicAbstractObject, ord... As %String)
	i obj.%Extends("%DynamicObject") {
		s new={}, itr=obj.%GetIterator()
		i '$g(ord) {
			while itr.%GetNext(.k) { s done(k)=0 }
			s k="" f  s k=$o(done(k)) q:k=""  d new.%Set(k,obj.%Get(k))
		} else {
			f i=1:1:$g(ord) { s k=ord(i),done(k)=1 d:$e(obj.%GetTypeOf(k),1,2)'="un" new.%Set(k,obj.%Get(k)) }
			while itr.%GetNext(.k,.v) { d:'$d(done(k)) new.%Set(k,v) }
	} elseif obj.%Extends("%DynamicArray") {
		s new=[], itr=obj.%GetIterator(), max=obj.%Size(), done=""
		f i=1:1:$g(ord) { s k=ord(i) i k,k<=max d new.%Push(obj.%Get(k-1)) s $bit(done,k)=1 }
		while itr.%GetNext(.k,.v) { d:'$bit(done,k+1) new.%Push(v) }
	} else { s new=obj }
	q new

Some examples

s car={"color":"red", "fuel":"diesel", "maxspeed":150, "maker":"Audi", "model":"Quattro Q5", "power":300, "available":true, "rating":8, "allWheel":true }
s car1=##class(DC.Utility).ReOrder(car) // order all props alphabetically
s car2=##class(DC.Utility).ReOrder(car,"maker","model","available") // start with maker, model, etc.

w car.%ToJSON(),!,car1.%ToJSON(),!,car2.%ToJSON() --->
{"color":"red","fuel":"diesel","maxspeed":150,"maker":"Audi","model":"Quattro Q5","power":300,"available":true,"rating":8,"allWheel":true}
{"allWheel":"1","available":"1","color":"red","fuel":"diesel","maker":"Audi","maxspeed":150,"model":"Quattro Q5","power":300,"rating":8}
{"maker":"Audi","model":"Quattro Q5","available":"1","color":"red","fuel":"diesel","maxspeed":150,"power":300,"rating":8,"allWheel":"1"}

Thanks, Julius, that is really helpful!!

I have implemented the part of the method that I needed as follows:

/// Move FHIR resourceproperties in the followin order:
/// - resourceType
/// - id
/// - meta
/// - extension
ClassMethod FHIROrderResourceProperties(resource As %DynamicObject) As %DynamicObject
    #dim order as %DynamicArray = [ "resourceType", "id", "meta", "extension" ]
    #dim newObject as %DynamicObject = {}

    for index = 0:1:order.%Size() - 1
        set element = order.%Get(index)
        set done(element) = 1

        if $EXTRACT(resource.%GetTypeOf(element), 1, 2) '= "un"
            do newObject.%Set(element, resource.%Get(element)) 
    set iterator = resource.%GetIterator()

    while iterator.%GetNext(.element, .value)
        if '$DATA(done(element))
            do newObject.%Set(element, value)

    return newObject