# About ValueTree::valueTreeChildOrderChanged

**URL:** <https://forum.juce.com/t/about-valuetree-valuetreechildorderchanged/60505>\
**Category:** General JUCE discussion\
**Created:** [March 19, 2024, 8:38am UTC](https://forum.juce.com/t/about-valuetree-valuetreechildorderchanged/60505 "2024-03-19T08:38:04Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![Kraku](https://avatars.discourse-cdn.com/v4/letter/k/74df32/32.png) [@Kraku](https://forum.juce.com/u/Kraku)\
**Post date:** [March 19, 2024, 8:38am UTC](https://forum.juce.com/t/about-valuetree-valuetreechildorderchanged/60505/1 "2024-03-19T08:38:04Z")

</div>

Let’s say I have ValueTree called “node”.  
I listen to it’s changes with: node.addListener(this);  
Then I do the following:

```auto
        node.addChild(juc::ValueTree(blah), 0, nullptr);
        node.addChild(juc::ValueTree(blah), 1, nullptr);
        node.addChild(juc::ValueTree(blah), 0, nullptr);

```

As expected, ValueTree::Listener::valueTreeChildAdded() gets called for each of those three rows.

However, I would assume that ValueTree::Listener::valueTreeChildOrderChanged() would get called after the last row, which adds a new child node infront of all the previous nodes. So I would assume ValueTree::Listener::valueTreeChildOrderChanged() would get called twice. But it doesn’t get called at all.

What do I don’t understand of the ValueTree’s basic behavior?

---

<div class="post-metadata">

**Author:** ![Kraku](https://avatars.discourse-cdn.com/v4/letter/k/74df32/32.png) [@Kraku](https://forum.juce.com/u/Kraku)\
**Post date:** [March 20, 2024, 1:36pm UTC](https://forum.juce.com/t/about-valuetree-valuetreechildorderchanged/60505/2 "2024-03-20T13:36:21Z")

</div>

Another oddity I just noticed is the following:

```auto
    juce::ValueTree nodeA(typeAID);
    juce::ValueTree nodeB(typeBID);
    juce::ValueTree nodeC(typeCID);

    nodeA.addListener(this);

    nodeB.appendChild(nodeC, pUndoManager);
    nodeA.appendChild(nodeB, pUndoManager);

```

What happens is that at the last code line above ValueTree::Listener::valueTreeChildAdded() gets called as it should be. But what is weird is that it gets called twice instead of once. Both times the parameters seem to be the same:

```auto
parentTree = nodeA
childWhichHasBeenAdded = nodeB

```

I would expect one of the following to happen:

1. The listener method gets called only once with the above parameters.
2. The #1 happens and in addition also the same method gets called with nodeB and nodeC as its parameters. So the method would be called twice in total.

Is this the intended behavior or is there a bug or am I doing something wrong?

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<div class="post-metadata">

**Author:** ![jellebakker](https://sea2.discourse-cdn.com/flex026/user_avatar/forum.juce.com/jellebakker/32/17053_2.png) [@jellebakker](https://forum.juce.com/u/jellebakker)\
**Post date:** [March 20, 2024, 7:40pm UTC](https://forum.juce.com/t/about-valuetree-valuetreechildorderchanged/60505/3 "2024-03-20T19:40:57Z")

</div>

About your first question:  
Adding a child at the beginning doesn’t change the order. Therefore, `ValueTree::Listener::valueTreeChildOrderChanged` is not called. It will be called when you explicitly change the order with `ValueTree::moveChild`.

About your second question:  
If I run your code, it only calls `ValueTree::Listener::valueTreeChildAdded` once. I tested this with the code below (which is the same as your code but slightly modified).

```auto
struct Listener : juce::ValueTree::Listener
{
    void valueTreeChildAdded (juce::ValueTree &parentTree, juce::ValueTree &childWhichHasBeenAdded)
    {
        DBG("valueTreeChildAdded");
    }
};
Listener listener;

juce::ValueTree nodeA("typeAID");
juce::ValueTree nodeB("typeBID");
juce::ValueTree nodeC("typeCID");

nodeA.addListener(&listener);

nodeB.appendChild(nodeC, nullptr);
nodeA.appendChild(nodeB, nullptr);

// Output:
// valueTreeChildAdded

```

---

<div class="post-metadata">

**Author:** ![Kraku](https://avatars.discourse-cdn.com/v4/letter/k/74df32/32.png) [@Kraku](https://forum.juce.com/u/Kraku)\
**Post date:** [March 21, 2024, 9:03am UTC](https://forum.juce.com/t/about-valuetree-valuetreechildorderchanged/60505/4 "2024-03-21T09:03:27Z")

</div>

OK, these helped me figure out what was wrong with my code. Thanks!

Regarding the first question:  
I thought “order changed” was the same as “child index changed”, but those are actually conceptually two different things. Makes sense now.

Regarding the second question:  
I found an extra addListener(this) to a parent ValueTree from my code. So the same class was registered as a listener to two different hierarchy levels for the ValueTrees. That’s what caused the weirdness.