how do i check if an object has a parent

Question

hello everyone, i want to be able to check if this object has a parent, if so i want it to do send some messages to that parent, but that object could also have no parent, in which case i want it to do carry out other functions. but not sending messages to its parent. The first thing i came up with was the following

 if (transform.parent.parent != null){
     transform.parent.sendMessage("bla bla");
 }

that for some reason is giving me a null reference exeption on the first line of the if statement. i have no idea what to try next. any help is much apreciated. thank you all in advanced

Answer 1

Answer by homer_3 · Feb 13, 2014 at 11:19 PM

If you are checking for both the parent and parent's parent

 if (transform.parent != null && transform.parent.parent != null){
     transform.parent.sendMessage("bla bla");
 }

Also, the order of this check matters.

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thenachotech1113 · Feb 13, 2014 at 11:22 PM 0

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thank you, i have been cracking my head all day, but i just noticed as i read your answer, if it has no parent, there is no way on earth it could have a parent's parent.

ElijahShadbolt thenachotech1113 · Nov 15, 2016 at 05:37 AM 0

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[$$anonymous$$ake it best answer] :)

tanamu · Apr 08, 2018 at 11:04 AM 2

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This answer helped me when I tried to check if parent exist by calling transform.parent.gameObject. Calling gameObject like this rises an exception, but if I check transform.parent != null before calling transform.parent.gameObject, everything will be fine. Thanks!

Answer 2

Answer by ElijahShadbolt · Jan 27, 2017 at 07:06 AM

For a recursive algorithm:

 Transform parent = transform.parent;
 int i = 1;
 while (parent != null)
 {
     Debug.Log("Reached parent " + i + ": " + parent.name);
     parent.SendMessage("example");
 
     parent = parent.parent;
     ++i;
 }
 Debug.Log("No more parents");

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NoseKills · Jan 27, 2017 at 07:44 AM 0

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Definitely a better, more generic answer than the "current best".

I would just change this so "parent" isn't left null at the end like it is now (if there is at least 1 non null parent). Then you could make this a general purpose method that returns the root-most parent if any.

ElijahShadbolt · Jan 28, 2017 at 07:14 AM 0

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@Nose$$anonymous$$ills Like so:

 Transform parent = transform.parent;
 if (parent != null)
 {
     int i = 1;
     while (true)
     {
         Debug.Log("Reached parent " + i + ": " + parent.name);
         parent.Send$$anonymous$$essage("...");
 
         if (parent.parent != null)
         {
             parent = parent.parent;
             ++i;
         }
         else
         {
             break;
         }
     }
     Debug.Log("Root object is " + parent.name);
 }
 else
 {
     Debug.Log("This object has no parents");
 }

Answer 3

If you have 1 object whit 1 parent and chef for the parent 2, no problem, but if check for parent 3 you recive error because 2 no exist, then you can do:

 if (transform.parent)
         {
             Debug.Log("you have 1 parent");
             if (transform.parent.parent)
             {
                 Debug.Log("you have 2 parents");
                 if (transform.parent.parent.parent)
                 {
                     Debug.Log("you have 3 parents");
                     if (transform.parent.parent.parent.parent)
                     {
                         Debug.Log("you have 4 parents");
                         if (transform.parent.parent.parent.parent.parent)
                         {
                             Debug.Log("you have 5 parents");
                             if (transform.parent.parent.parent.parent.parent.parent)
                             {
                                 Debug.Log("you have 6 parents, ask to mama");
                                 // etc...
                             }
                         }
                     }
                 }
             }
         }

Answer 4

Answer by unity_24westk · May 02, 2018 at 11:10 PM

looks like we got a code Egyptian.

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Answer 5

Answer by onetimepad · yesterday

Check if A is a parent of B

 bool ParentCheck(Transform childTransform, Transform parentTransform){
     if(childTransform.parent!=null){
         if(childTransform.parent.transform==parentTransform){
             return true;
         }else{
             return ParentCheck(childTransform.parent,parentTransform);
         }
     }else{
         return false;
     }
 }

Also childTransform.IsChildOf(parentTrasform) will give

true if this transform is a child, deep child (child of a child) or identical to this transform, otherwise false.

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Bunny83 · yesterday 0

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You should avoid such nesting if if statements. It makes the code less readable. Also parent.transform is pretty pointless since "parent" is a transform and getter the transform of a transform is redundant. I would suggest a method like this:

 public static bool IsChildOf(this Transform childTransform, Transform parentTransform)
 {
     if(childTransform.parent == null)
         return false;
     if(childTransform.parent == parentTransform)
         return true;
     return IsChildOf(childTransform.parent, parentTransform);
 }

Now the code is linear with 3 destinct exits. Utility functions like that should be static so they can be reused much easier. I also made it an extension method (has to be declared in a static class for this). As n extension method you can simply do

 if (someObj.IsChildOf(someParent))

Since "childTransform.parent" is used 3 times inside the method I would probably create a localv variable for it. It would shorten the lines a bit and also improve performance slightly. Reading the parent actually grabs the parent info out of the native code, So caching it locally would be common.

how do i check if an object has a parent

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