Check out example codes for "unity getcomponent". It will help you in understanding the concepts better.

Code Example 1

//First script 
public class Enemy : MonoBehaviour{
  public int health = 10;
  public void saySomething(){
    Debug.Log("Hi, i am an enemy.");
  } 
}
//Second script
//There is one thing though,
//if the script is located on another gameobject,
//which will be most likely, you have to somehow
//find that gameobject first. There are many ways of
//doing it, via raycast, collision,
//trigger, find by tag, find by gameobject etc.
//But i will use the simplest way to understand,
//that is declaring public GameObject in player script,
//which contains Enemy, and later you just drag and drop the
//gameobject in the inspector.
public class Player : MonoBehaviour{
  //Drag and drop gameobject with script Enemy in inspector
  GameObject enemyGameObject;
  void Start(){       
    //We get Enemy component - script
    //from public gameobject which contains this script
    Enemy enemyScript = enemyGameObject.GetComponent<Enemy>();
    //This will debug Enemy health is: 10  
    Debug.Log("Enemy health is:"+ enemyScript.health)  
      //This will debug "Hi, i am an enemy." 
      enemyScript.saySomething();  
  } 
}

Code Example 2

using UnityEngine;

public class TryGetComponentExample : MonoBehaviour
{
    void Start()
    {
    	// Since Unity  2019.2 you can use TryGetComponent to check
        // if an object has a component, it will not allocate GC in 
        // the editor if the object doesn't have one.
        if (TryGetComponent(out Rigidbody rigidFound))
        {
        	// Deactivate rigidbody
            rigidFound.enabled = false;
        }
        
		// For versions below 2019.2 you can do it this way:
        // Create a variable
        Rigidbody rigidFound = GetComponent<Rigidbody>();
        
        // If the 'Rigidbody' exist in the gameobject
        if(rigidFound != null)
        {
        	// Deactivate rigidbody
            rigidFound.enabled = false;
        }
	}
}

Code Example 3

GetComponent<Rigidbody>(); //used to find component on character (rigid body can be changed)
GameObject.FindGameObjectWithTag("player"); //finds any game object in the scene with this tag

Code Example 4

public GameObject Var; //only if the component you want is on a different gameObject

void Start(){
	Var.GetComponent<Component>(); //just GetComponent<Component>(); if the component you want is on the same object as script
}

Code Example 5

rb = GetComponent<Rigidbody>();

Code Example 6

using UnityEngine;public class GetComponentExample : MonoBehaviour
{
    void Start()
    {
        HingeJoint hinge = gameObject.GetComponent(typeof(HingeJoint)) as HingeJoint;        if (hinge != null)
            hinge.useSpring = false;
    }
}

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