Convert ValueTree to DynamicObject?

General JUCE discussion
1

Is there an easy way to convert ValueTree to DynamicObject and back?

I’m creating an app with javascript and I need to manipulate / pass around value tree stuff between C++ and Javascript. I want to manipulate a value tree with javascript.

I guess the main issue is I want to store a value tree child inside a var.

Edit: The one way I can think of is storing ValueTree as an xml String var for javascript, and then converting xml back to value tree for c++. But that would suck because then I couldn’t do things like:

item = itemlist.getItem(0); myName = item.name;

It would have to be:

item = itemlist.getItem(0); myName = xmlThing.getProperty("NAME", item);

Edit: Hmm, another problem is setting the name. If I set the name the valuetree needs to be updated:

itemlist.getItem(0).setName("newname");

If I can’t update it with that kind of method call, then I need to do:

itemlist.setItemName(0, "newname");

unless of course I create many methods, many object types, and many properties for every possibility to communicate between C++ ValueTree and javascript objects.

1 Like
2

I am using a similar concept for converting the ValueTree of my UI objects into a JSON representation:

<Component type="ScriptPanel" id="Panel1" x="156" y="94" width="373" height="302">
  <Component type="ScriptSlider" id="Knob1" x="84.00000000" y="116.00000000"
             parentComponent="Panel1"/>
  <Component type="ScriptSlider" id="Knob2" x="128.00000000" y="33" parentComponent="Panel1"
             width="198.00000000"/>
</Component>

becomes this:

{
  "type": "ScriptPanel",
  "id": "Panel1",
  "x": 156,
  "y": 94,
  "width": 373,
  "height": 302,
  "childComponents": [
    {
      "type": "ScriptSlider",
      "id": "Knob1",
      "x": 84.0,
      "y": 116.0,
      "parentComponent": "Panel1"
    },
    {
      "type": "ScriptSlider",
      "id": "Knob2",
      "x": 128.0,
      "y": 33,
      "parentComponent": "Panel1",
      "width": 198.0
    }
  ]
}

You might notice that I don’t care about the tag name of the XML at all - they’re all named Component. Also you need to introduce a artificial property that holds the child elements in a list.

Now as far as the implementation goes, you can’t operate on the actual ValueTree object directly - unless you subclass DynamicObject and it’s getter / setter methods, but I am not sure if this works. So you definitely need some kind of flush function:

var myObject = ValueTreeClass.get("myFunkyTree");
myObject.name = "newName";
ValueTreeClass.flush("myFunkyTree", myObject);

First line converts ValueTree to DynamicObject, second line does some operation and the third line writes the DynamicObject back to the value tree.

1 Like
3

I’m trying to create valueTreeToVar recursive function, but I’m stuck. Not sure how to add children. Only got the properties so far.

var valueTreeToVar(ValueTree& node, var& result)
{
	for (auto i = 0; i < node.getNumProperties(); ++i)
	{
		auto propertyName = node.getPropertyName(i);
		auto propertyValue = node.getPropertyPointer(propertyName);

		result.getDynamicObject()->setProperty(propertyName, propertyValue);
	}

	for (auto i = 0; i < node.getNumChildren(); ++i)
	{
		auto id = node.getChild(i).getType();

		result.getDynamicObject()->setProperty(id, {});

		valueTreeToVar(node.getChild(i), result);
	}

	juce::MemoryOutputStream stream;

	result.getDynamicObject()->writeAsJSON(stream, 0, false);
	DBG(stream.toString());

	return result;
}
4

You’re almost there. Just pass in the child object into the recursive function call to build up the tree:

void valueTreeToVar(const ValueTree& node, var& result)
{
    static const Identifier id_("id");
    result.setProperty(id_, node.getType().toString());

	for (auto i = 0; i < node.getNumProperties(); ++i)
	{
		auto propertyName = node.getPropertyName(i);
		auto propertyValue = node.getPropertyPointer(propertyName);

		result.getDynamicObject()->setProperty(propertyName, propertyValue);
	}

    // this will hold our elements
    Array<var> childList;

     // you can use the iterator loop for child value trees.
	for (const auto& child: node) 
	{
        var childObject(new DynamicObject());

		// You don't need to do this here, the id will be set 
        // in the recursive function call 
        //result.getDynamicObject()->setProperty(id, {});

        valueTreeToVar(child, childObject);
        childList.add(childObject);
	}

    static const Identifier children_("children");
    result.setProperty(children_, childList);

}

The debugging code has to be moved outside of the recursive function or it will get executed for every child element.

DISCLAIMER: I typed the code in here, there might be some silly typos.

5

The debugging code has to be moved outside of the recursive function or it will get executed for every child element.

that’s the point!

Thanks for the help.

6

So now I’m having trouble using the var. I get a crash because I think the dynamicObject is getting deleted.

static var valueTreeToVar(const var::NativeFunctionArgs& args)
{
	RppReader rppReader(args.arguments[0].toString());

	DynamicObject dynamicObject;

	var returnVar(&dynamicObject);

	rppReader.valueTreeToVar(rppReader.getValueTree(), returnVar);

	return returnVar;
}
7

It’s absolutely getting deleted. It would behoove you to understand ‘scope’ as it relates to the lifetimes of objects. But, to get you going, you want:

var returnVar (new DynamicObject)

1 Like
9

How do you convert var back to ValueTree?

p.s. this is working code for valueTreeToVar, the original code before this post has a few mistakes I think.

void RppProject::valueTreeToVar(ValueTree node, var& result)
{
	result.getDynamicObject()->setProperty("id", node.getType().toString());

	for (auto i = 0; i < node.getNumProperties(); ++i)
	{
		auto propertyName = node.getPropertyName(i);
		auto propertyValue = node.getPropertyPointer(propertyName)->toString();

		result.getDynamicObject()->setProperty(propertyName, propertyValue);
	}

	Array<var> childList;

	for (int i = 0; i < node.getNumChildren(); ++i)
	{
		const auto& child = node.getChild(i);

		var childObject(new DynamicObject());
		valueTreeToVar(child, childObject);

		childList.add(childObject);

		result.getDynamicObject()->setProperty("children", childList);
	}
}
10

Here is some code that might be a starting point. It’s still an early on in it’s implementation, in that I just codified it a few weeks ago, to help me process JSON input. But I think the basic ‘tree walking’ structure of it will help you build some code to make ValueTree’s.

VarHelpers.h

#pragma once

#include "../JuceLibraryCode/JuceHeader.h"

namespace VarHelpers
{
    void addProperty (const var& object, String key, var value);
    var addSection (const var& object, String key);
    void forEachSection (const var& object, std::function<void (String key, const var& section)> sectionCallback);
    void forEachProperty (const var& object, std::function<void (String key, const var& property)> propertyCallback);
    String getVarAttribString (const var& theVar);
    void dumpVar (const var& theVar);
    const var& getSection (const var& theVar, Identifier key);
        
    template<class T>
    bool hasProperty (const var& theVar, Identifier property)
    {
        if (theVar.hasProperty (property))
        {
            if constexpr (std::is_same_v<T, int>)
            {
                if (theVar[property].isInt ())
                    return true;
            }
            else if constexpr (std::is_same_v<T, int64>)
            {
                if (theVar[property].isInt64 ())
                    return true;
            }
            else if constexpr (std::is_same_v<T, bool>)
            {
                if (theVar[property].isBool ())
                    return true;
            }
            else if constexpr (std::is_same_v<T, double>)
            {
                if (theVar[property].isDouble ())
                    return true;
            }
            else if constexpr (std::is_same_v<T, String>)
            {
                if (theVar[property].isString ())
                    return true;
            }
            else if constexpr (std::is_same_v<T, Array<var>>)
            {
                if (theVar[property].isArray ())
                    return true;
            }
        }
        return false;
    }

    template<class T>
    T getProperty (const var& theVar, Identifier property)
    {
        if constexpr (std::is_same_v<T, String>)
            return theVar[property].toString ();
        else
            return (T)theVar[property];
    }
};

VarHelpers.cpp

#include "VarHelpers.h"

namespace VarHelpers
{
    void addProperty (const var& object, String key, var value)
    {
        if (!key.isEmpty () && object.isObject ())
            object.getDynamicObject ()->setProperty (key, value);
    };

    var addSection (const var& object, String key)
    {
        if (!key.isEmpty () && object.isObject ())
        {
            var newSection (new DynamicObject);
            addProperty (object, key, newSection);
            return newSection;
        }

        return {};
    }

    void forEachSection (const var& object, std::function<void (String key, const var& section)> sectionCallback)
    {
        if (object.isObject ())
        {
            const auto dynamicObject = object.getDynamicObject ();
            const auto namedPropertySet = dynamicObject->getProperties ();
            for (const auto& namedProperty : namedPropertySet)
            {
                if (namedProperty.value.isObject ())
                    sectionCallback (namedProperty.name.toString (), namedProperty.value);
            }
        }
    }

    void forEachProperty (const var& object, std::function<void (String key, const var& property)> propertyCallback)
    {
        if (object.isObject ())
        {
            const auto dynamicObject = object.getDynamicObject ();
            const auto namedPropertySet = dynamicObject->getProperties ();
            for (const auto& namedProperty : namedPropertySet)
            {
                if (!namedProperty.value.isObject ())
                    propertyCallback (namedProperty.name.toString (), namedProperty.value);
            }

        }
    }

    String getVarAttribString (const var& theVar)
    {
        if (theVar.isVoid ())
            return "void";
        else if (theVar.isInt ())
            return "int";
        else if (theVar.isInt64 ())
            return "int64";
        else if (theVar.isBool ())
            return "bool";
        else if (theVar.isDouble ())
            return "double";
        else if (theVar.isString ())
            return "String";
        else if (theVar.isObject ())
            return "Object";
        else if (theVar.isArray ())
            return "Array";
        else if (theVar.isBinaryData ())
            return "BinaryData";
        else if (theVar.isMethod ())
            return "Method";

        return "unknown";
    };

    void dumpVar (const var& theVar)
    {
        if (theVar.isObject())
        {
            std::function<void (const var& theVar, String name, int indentLevel)> dumpSections = [&dumpSections](const var& theVar, String name, int indentLevel)
            {
                Logger::outputDebugString (String (std::string (indentLevel, ' ')) + String ("<") + (name.isEmpty () ? String ("noname") : name) + String (">"));
                VarHelpers::forEachProperty (theVar, [indentLevel](String key, const var& value)
                    {
                        Logger::outputDebugString (String (std::string (indentLevel + 1, ' ')) + key + " : " + VarHelpers::getVarAttribString (value));
                    });
                VarHelpers::forEachSection (theVar, [&dumpSections, indentLevel](String key, const var& value)
                    {
                        dumpSections (value, key, indentLevel + 1);
                    });
            };
            dumpSections (theVar, "", 0);
        }
        else
        {
            Logger::outputDebugString ("var type : " + VarHelpers::getVarAttribString (theVar));
        }
    }

    const var emptyVar;

    const var& getSection (const var& theVar, Identifier key)
    {
        if (const auto& section = theVar[key]; section.isObject ())
            return section;
        else
            return emptyVar;
    }
};
1 Like