# DynamicObject's getProperty not being called in JavaScript engine

**URL:** <https://forum.juce.com/t/dynamicobjects-getproperty-not-being-called-in-javascript-engine/13642>\
**Category:** General JUCE discussion\
**Created:** [September 29, 2014, 7:35am UTC](https://forum.juce.com/t/dynamicobjects-getproperty-not-being-called-in-javascript-engine/13642 "2014-09-29T07:35:38Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![rebbur](https://avatars.discourse-cdn.com/v4/letter/r/ecae2f/32.png) [@rebbur](https://forum.juce.com/u/rebbur)\
**Post date:** [September 29, 2014, 7:35am UTC](https://forum.juce.com/t/dynamicobjects-getproperty-not-being-called-in-javascript-engine/13642/1 "2014-09-29T07:35:38Z")

</div>

Hi Jules,  
I have some issues with the DynamicObject class in JavaScript.  
I'm trying to bridge my own Param system to Javascript using DynamicObjects. What i would like to do is forward calls on invoked DynamicObjects&nbsp;&nbsp;to my params object. See code at the end of the post.

This works fine when setting properties, so that when a user types in Params.scale = 10; It will call setProperty and i'll forward it to param-\>setValue, and call the base method as well.

This does not work when reading properties. So i can't do this var scale = Params.scale; &nbsp;In the JavaScript engine&nbsp;getProperty won't be called because it uses getProperties, which just directly access the NameValueSet.&nbsp;

```
if (var* prop = o->getProperties().getVarPointer (functionName))

                    return *prop;
```

&nbsp;

So my question is, why isn't getProperty being called instead of getProperties().getVarPointer()?  
If you would call getProperty it would allow us to have much more flexibility.

&nbsp;

```
​
class JSParams : public DynamicObject
{
private:

ra::ParamContainer::Ptr params;

public:

    JSParams(ra::ParamContainer::Ptr params_)

        : params(params_)

    {

    }
    
    static Indentifier getClassName()
    {
       static const Identifier i("Params");
       return i;
    }

    bool hasProperty (const Identifier& propertyName) const
    {
        return params->getParam(propertyName.toString()) != nullptr;
    }

    var getProperty (const Identifier& propertyName) const
    {
         //this never get's called!
        ra::ParamBase::Ptr param = params->getParam(propertyName.toString());
        return param->getValue();

    }

    void setProperty (const Identifier& propertyName, const var& newValue)
    {
        //this get's called
        ra::ParamBase::Ptr param = params->getParam(propertyName.toString());
        param->setValue(newValue);
        DynamicObject::setProperty(propertyName, newValue);
    }

};
```

---

<div class="post-metadata">

**Author:** ![jules](https://avatars.discourse-cdn.com/v4/letter/j/41988e/32.png) [@jules](https://forum.juce.com/u/jules)\
**Post date:** [September 29, 2014, 8:47am UTC](https://forum.juce.com/t/dynamicobjects-getproperty-not-being-called-in-javascript-engine/13642/2 "2014-09-29T08:47:58Z")

</div>

It's done like that because it needs to very quickly find out whether a property exists or not, and if it does, to get its value.

When I wrote it, I obviously wasn't thinking about custom objects that might have overrides, I was just writing the most efficient code that I could, because this is a&nbsp;method that needs to be fast to get decent performance.

I just began a bit of refactoring, thinking that if DynamicObject::getProperty returned a var\* instead of a var, then that might do the trick, but to do that opens a can of worms that I don't have time to get dragged into right now. I think the whole set of get/set methods for DynamicObject probably needs a re-think as the class is being used in some new ways that weren't planned-for when I first created it.

---

<div class="post-metadata">

**Author:** ![rebbur](https://avatars.discourse-cdn.com/v4/letter/r/ecae2f/32.png) [@rebbur](https://forum.juce.com/u/rebbur)\
**Post date:** [September 29, 2014, 1:07pm UTC](https://forum.juce.com/t/dynamicobjects-getproperty-not-being-called-in-javascript-engine/13642/3 "2014-09-29T13:07:00Z")

</div>

Allright, in the mean time i've found a workaround for own usecase.

A possible solution could be to&nbsp;create a getPropertyWithDefault(const Identifier& name, var default = var::null); method like you did with the&nbsp;NamedValueSet::getWithDefault

It will check internally and return the right value when it's there, otherwise it'll return var::null; So the default implementation&nbsp;can still be very fast.

I'll see what you can come up with in the end&nbsp;

&nbsp;