How to check if OnDestroy has finished?

I have a script that adds a LineRenderer to the parent GameObject. When I try to destroy and readd that script to the same GameObject, it will tell me that the script can not add a LineRenderer because the old one has not been destroyed yet, even though I destroy the LineRenderer component in the OnDestroy function.

My Code:

The function that readds the component:

 void OnWeaponBehaviourUpdate(string weaponBehaviourName){
     Destroy(weaponInstance.GetComponent(weaponBehaviourStringOld));
     weaponInstance.AddComponent(weaponBehaviourString);
 }

(weaponBehaviourStringOld == weaponBehaviourString)

And this is the OnDestroy function in the readded script:

 void OnDestroy(){
     Destroy (lineRenderer);
 }

I hope I have gave you enough code and look forward to an answer!

Thanks in advance, Xera