Check if a GameObject has a certain script

I want to make a function to see if a gameObject has a certain script attached.

I remember seeing some time ago how to pass a reference of any type, it was something with T or <t>, I'm quite sure this is something to do with Collections, but I am a bit confused about it and cant remember how to work with it.
Maybe thats not even the best approach so any advices are of great help =]

Here is part of the function that I will use to get the components attached to the gameObject and check if one of the components is of the same type as the class of the script I am looking for

Code (csharp):

1.  
2.     public static bool HasComponent(GameObject obj, TheScriptClass scriptClassParam)
3.     {
4.         Component[] cs = (Component[])obj.GetComponents(typeof(Component));
5.         foreach (Component c in cs)
6.         {
7.             Debug.Log("name " + c.name + " type " + c.GetType() + " basetype " + c.GetType().BaseType);
8.            
9.             //this part is where I want to check with the class that was passed to the function as a parameter
10.             if (c.GetType() == scriptClassParam)
11.             {
12.                 return true;
13.             }
14.  
15.         }
16.         return false;
17.     }
18.  

Oh btw, can anyone tell me if a for each loop any faster or slower then the GetComponent<type>() function?

Thanks

 

if you know exactly what type of component you want to check if its there, why not something really simple like

JS
if(gameObject.GetComponent("YouDesiredScript") != null)

C#
if((gameObject.GetComponent("YourDesiredScript") as YourDesiredScript) != null)

i have used that simple method for finding out if a specific object has a specific script attached

hope this helps

 

Hi Hermes, gracias por tu respuesta

I know this is very similar to the GetComponent<Script>() , I also use the GetComponent function sometimes.
The reason I want to do this is because I want to expand my function to check multiple scripts at once passing a String array in another variation of this function, this one is just one of the helper functions I am creating.

There will be different variations of this function with other parameters, but the base of it is the same as GetComponent that checks if there is a certain script attached.


I found a way to do that, the base of the function is below, if anyone is interested in doing something similar one day here you go:

Code (csharp):

1.  
2.     public static bool HasComponent(GameObject obj, Type ClassType )
3.     {
4.         Component[] cs = (Component[])obj.GetComponents(typeof(Component));
5.         foreach (Component c in cs)
6.         {
7.  
8.             if (c.GetType() == ClassType)
9.             {
10.                 return true;
11.             }
12.  
13.         }
14.         return false;
15.     }
16.  

and to call the function:

Code (csharp):

1. HasComponent(MyGameObject,Type.GetType("Enemy")

Where MyGameObject is the gameObject on the scene that I want to check, and the "Enemy" is the name of the class and script that is attached to it that I want to check

 

Kinda late, but I'm trying to solve this too. When I use your method I get a MissingComponentException if it doesn't have the component, and I would like to avoid this. Is there any way to do that?

 

Nevermind, did

if(gameObject.GetComponents<YourDesiredComponent>().Length != 0)

Instead

 

Code (CSharp):

1. using System.Linq;
2.  
3. public static bool HasComponent<T>(this GameObject go) where T : Component
4.         {
5.             return go.GetComponentsInChildren<T>().FirstOrDefault() != null;
6.         }

 

I don't understand why you would bother doing any of the stuff mentioned in this thread.

Code (csharp):

1.  
2. SomeScript ss = GetComponent<SomeScript>();
3. if (ss != null)
4. {
5.     DoGreatThings();
6. }
7.  

 

^it wont check if it is attached to specific GO though

 

Ok? So just ask that GameObject instead of the current one

Code (csharp):

1.  
2. var script = someGameObject.GetComponent<SomeScript>();
3. if (script != null)
4. {
5.  
6. }
7.  

 

This will return exception if GO does not exist in the scene

 

No it won't. Also maybe don't necro three years old threads to complain about stuff that works?

 

It will if the GameObject itself doesn't exist - but again, this is all standard stuff. Check if your thing is null before attempting to do something with it. Plain and simple, and none of the other solutions posted would resolve that issue either.

 

Yes it will:

A simple check returns exception if scene has no specified gameObject and IF your check is to check if go exist.

That's the thing mate - if you try to check for null specific gO with specific Component and said gO does not exist in the scene - you are ded. All dies here.

 

Frankly I have absolutely no idea what you're talking about. If it is possible for a particular GameObject that you care about to be destroyed or otherwise become null during gameplay then you should null check it before operating on it.

 

Even if it is not destroyed and active and in the scene. If an object has no component you request the nullref exception will be thrown in if{} REGARDLESS.
Been over this for weeks had to resort to some custom functions for that

 

No it doesn't. It only throws a NullReferenceException if you attempt to access something in that component without null checking it. If the GameObject is not null this will work all day long

Code (csharp):

1.  
2. if (notNullGo.GetComponent<NullComponent>() != null)
3. {
4.     // if notNullGo is not null and it has no NullComponent attached this will never execute
5. }
6.  

 

Ummm. What? Are you trying to say null checking is broken? This kind of thing doesn't happen, this is entirely user error on your part. Here is a simple check if a component exists on a GameObject

Code (CSharp):

1. if(theGameObject != null && theGameObject.GetComponent<TheComponent>() != null){
2.     // the component exists
3. } else {
4.     // the component does not exist
5. }

 

Which one of these people probably knows more about Unity...?

 

This one just boils down to common sense. A null check throwing a null ref would be about the dumbest design decision this side of a screen door on a submarine.

And honestly - RTFM. Right here: https://docs.unity3d.com/ScriptReference/GameObject.GetComponent.html

null if it doesn't.

If GetComponent returns null then that component isn't attached to the GameObject you're calling it on. That's how you determine if a GameObject has a specific component. Full stop. End of story.

 

I think this is the most readable way to do the same

Code (CSharp):

1. if(SomeGameObject?.GetComponent<Desired_Script>())
2. {
3.     // SomeGameObject is not null and it has Desired_Script component.
4. }

 

You should not use null conditional/propagating operators with UnityEngine.Object's. It bypasses the overridden

==

operator they use.

Seriously, it's 2023, we've had

TryGetComponent<T>(out T)

for years now.