Rotate and scale an object with speed over time

Question

I am trying to scale and rotate an object. The rotation is on X-Axis. I am able to implement the scale perfectly, it is the rotation that is causing the problem. How do I rotate the object to a target rotation and then back to initial rotation with this script? When I am executing this script, the rotation sometimes work and sometimes does not execute, however there is no problem with the scaling.

EDIT: The basic thing I found was that I cannot set Quaternion to negative value, that is -90 becomes 270 automatically and due to this I cannot move 270 to 0.

using UnityEngine;
using System.Collections;
 
 public class ScaleAndRotate : MonoBehaviour { 
     public int startSize = 3;
     public int minSize = 1;
     public int maxSize = 6;
     
     public float speed = 2.0f;
     
     private Vector3 targetScale;
     private Vector3 baseScale;
     private int currScale;

     //ROT

     public Quaternion targetRotation;
     public bool startRotation = false;
     
     void Start() {
         baseScale = transform.localScale;
         transform.localScale = baseScale * startSize;
         currScale = startSize;
         targetScale = baseScale * startSize;
     }
     
     void Update() {
         transform.localScale = Vector3.Lerp (transform.localScale, targetScale, speed * Time.deltaTime);

         if(startRotation == true)
         {
             transform.rotation = Quaternion.Slerp(transform.rotation, targetRotation, Time.deltaTime * speed);
         }
         else
         if(startRotation == false)
         {
             //Go Back To Initial Rotation
         }
         
 
         if (Input.GetKeyDown (KeyCode.UpArrow))
         {
             ChangeSize (true);
             startRotation = true;
         }
         if (Input.GetKeyDown (KeyCode.DownArrow))
         {
             ChangeSize (false);
             startRotation = false;
         }
     }
     
     public void ChangeSize(bool bigger) {
         
         if (bigger)
         {
             currScale++;
             
         }
             
         else
         {
             currScale--;
             
         }
             
         
         currScale = Mathf.Clamp (currScale, minSize, maxSize+1);
         
         targetScale = baseScale * currScale;
     }    
 }

Answer 1

The problem was with the transform.rotation that was not able to change the rotation from -90/270 to new rotation. I instead had to use transform.localRotation and it worked perfectly.

using UnityEngine;
using System.Collections;
 
 public class ScaleAndRotate : MonoBehaviour { 
     public int startSize = 3;
     public int minSize = 1;
     public int maxSize = 6;
     
     public float speed = 2.0f;
     
     private Vector3 targetScale;
     private Vector3 baseScale;
     private int currScale;

     //ROT

     public Quaternion targetRotation;
     public Quaternion initialRotation;
     public bool startRotation = false;
     
     void Start() {
         baseScale = transform.localScale;
         transform.localScale = baseScale * startSize;
         currScale = startSize;
         targetScale = baseScale * startSize;

         initialRotation = transform.localRotation;
     }
     
     void Update() {
         transform.localScale = Vector3.Lerp (transform.localScale, targetScale, speed * Time.deltaTime);

         if(startRotation == true)
         {
             transform.localRotation = Quaternion.Slerp(transform.localRotation, targetRotation, Time.deltaTime * speed);
         }
         else
         if(startRotation == false)
         {
             //Go Back To Initial Rotation
             transform.localRotation = Quaternion.Slerp(transform.localRotation, initialRotation, Time.deltaTime * speed);
         }
         
 
         if (Input.GetKeyDown (KeyCode.UpArrow))
         {
             ChangeSize (true);
             startRotation = false;
         }
             
         if (Input.GetKeyDown (KeyCode.DownArrow))
         {
             ChangeSize (false);
             startRotation = true;
         }
             
     }
     
     public void ChangeSize(bool bigger) {
         
         if (bigger)
         {
             currScale++;
             
         }
             
         else
         {
             currScale--;
             
         }
             
         
         currScale = Mathf.Clamp (currScale, minSize, maxSize+1);
         
         targetScale = baseScale * currScale;
     }    
 }

Answer 2

I think the problem is that you miss brackets when you use if statements:

         if (Input.GetKeyDown (KeyCode.UpArrow))
             ChangeSize (true);
             startRotation = true;
         if (Input.GetKeyDown (KeyCode.DownArrow))
             ChangeSize (false);
             startRotation = false;

When you use something like that code above the if is used only to the first following line of code. Thus, add brackets to that code:

if (Input.GetKeyDown (KeyCode.UpArrow))
{
             ChangeSize (true);
             startRotation = true;
}
         if (Input.GetKeyDown (KeyCode.DownArrow))
{
             ChangeSize (false);
             startRotation = false;
}