Introspection - getting class array in and out of JSON

I am trying to use introspection to serialise a hierarchical class structure for export via JSON - like a prefs file.
I seem to be OK with creating JSON strings for most properties, including primitives, dates, classes and arrays of primitives, but it all seems to fail with arrays of classes - I keep getting a TypeMismatchException when trying to assign the propertyInfo.value (which should be the array of classes) back to a locally dim’d array of the same classes e.g. as in

dim ss() as jsonRecord = pi.value(o)  //where pi is the propertyInfo, o is the object that the property sits in and jsonRecord is the expected class.

The strange thing is that I can export to JSON OK - the JSON.toString is fine. I can import that string to recreate the classes just fine - and all the classes are in their correct position/content etc. But when I try to re-export to JSON again I get the TypeMismatch error above. It is as if something in the re-creation of the classes hasn’t completed properly - perhaps in the constructor.invoke command in Introspection.constructorInfo.

Has anyone successfully done this that can share some code?

Yes. In fact, I have a whole open-source project to do just this:

Brilliant! Thanks Kem - looks comprehensive - I’ll let you know how I get on with it.

Well, it took a while but I eventually found the solution in your code (I couldn’t apply your classes directly as I wanted a different JSON format)

'// You can't go from a Variant that holds an array of some objects directly to '// an Object array, but you can go from an Auto that holds that array '// to an Object array. Am I exploiting a bug? Maybe, but it works. 'dim a as Auto = v 'dim arr() as Variant = a 'for i as integer = 0 to arr.Ubound 'elementsChild.Append ToJSONValue( arr( i ), "" ) 'next

The trick of loading the propertyInformation.value via an Auto before loading into a Variant did the trick and prevented the TypeMisMatch exception. In my code it looks like this:

[code] dim a as auto = pi.value(o) // - to avoid typeMismatchException after reload
dim ss() as variant = a

//need to cycle through the array to append each one.
for i as integer = 0 to ss.ubound
  js.value( str(i) ) = jsonRecord.get_json( ss(i), onlyPrefixed, compact)

A bug I think.

Shhh… :slight_smile: