Odd behaviour of SetParent or parent =

Unity Engine
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1

Hi there

I just noticed something weird

I tried setting the parent of object A to be object B

That didn’t work, object’s A parent never changed, I was like : wtf?

Then I took one more look at my code and the line after setting the parent of A to be B, I was setting the parent of B to be null

I didn’t think that would cause any sort of issue since why couldn’t A’s parent be B while B has no parent?

But hey, this is Unity we’re talking about, you cannot set A’s parent to be B if the line right after you set B’s parent to be null, right? Logical! Seriously, why? How’s that a problem for B to be A’s parent??

Unity devs??

So, solution is to FIRST set B’s parent to be null, THEN set A’s parent to be B, but WHY?

2

I was too. I think you have a bug. Unity works as expected. Try it yourself.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

// @kurtdekker - parenting - put this on a blank GameObject

public class Parenting : MonoBehaviour
{
    IEnumerator Start()
    {
        var A = new GameObject( "A");

        var B = new GameObject( "B");

// let's do it with .SetParent()
        B.transform.SetParent( this.transform);

        yield return new WaitForSeconds( 1.0f);

        A.transform.SetParent( B.transform);
        B.transform.SetParent(null);

        yield return new WaitForSeconds( 1.0f);

// now we'll do it with parent = 
        B.transform.parent = this.transform;
        A.transform.parent = null;

        yield return new WaitForSeconds( 1.0f);

        A.transform.parent = B.transform;
        B.transform.parent = null;
    }
}
3

Meaning it’s my code somewhere that is faulty or meaning there is a Unity bug but you cannot reproduce it?

I double checked my code see if there was anywhere else in any other script anything that would influence on that but I found not a single reference to my object A’s parent being set anywhere else than there

Very odd that just switching the line’s order makes it work, right?

4

Were you able to reproduce the problem with my code? Did I understand your claimed sequence correctly?

5

I haven’t tried it yet, I was sleeping :slight_smile:

Yes I think your code does what I explained

Not working code:

cameraHolder_transform.parent = helmet_instance.transform;
helmet_instance.transform.parent = null;

Working code:

helmet_instance.transform.parent = null;
cameraHolder_transform.parent = helmet_instance.transform;

In the first code snippet, the parent of cameraHolder doesn’t get set
In the second snippet, the parent is set properly
I tried both SetParent and parent =
Same results