· 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

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