How to inherit real-time data from parent class?

Questions & Answers
1

I have a an empty gameobject in the scene with RandomSpawn script attached to it. And I am spawning fishes in the scene. I have a float speed in RandomSpawn class which is public, and I can use it in the derived class from RandomSpawn. I am increasing the speed by Time.deltaTime in update method inside RandomSpawn. But I cannot see the updated speed while playing. How should I approach for updated speed being applied to every fish object I have created.

Here are my both scripts, first is RandomSpawn and second is Fish derived from RandomSpawn.

public class RandomSpawn : MonoBehaviour
{
    public GameObject[] fishPrefabs;
    [HideInInspector]public float speed = 3f;
    private float minSpawnInterval = 0.5f;
    private float maxSpawnInterval = 3f;
    private Vector3 spawnPos;
    public float zValue;
    // Start is called before the first frame update
    private void Start()
    {
        Invoke("Spawn", minSpawnInterval);
    }

    private void Update()
    {
        speed += 0.1f * Time.deltaTime;
    }

    void Spawn()
    {
        float time = Random.Range(minSpawnInterval, maxSpawnInterval);
        Invoke("Spawn", time);
        float xPos = 20;
        float randZ = Random.Range(-zValue, zValue);
        int fishIndex = Random.Range(0, fishPrefabs.Length);
        spawnPos = new Vector3(xPos, fishPrefabs[fishIndex].transform.position.y, transform.position.z + randZ);
        GameObject fishes = Instantiate(fishPrefabs[fishIndex], spawnPos, fishPrefabs[fishIndex].transform.rotation);
        Destroy(fishes, 15f);
    }
}


public class Fish : RandomSpawn
{
    Rigidbody rb;
    // Start is called before the first frame update
    void Start()
    {
        rb = GetComponent<Rigidbody>();
        
    }

    // Update is called once per frame
    void FixedUpdate()
    {
        rb.velocity = new Vector3(-speed, 0, 0);
    }

}
2

RE-EDIT:

To get the speed variable as a float value:

/// If using rigidbody 
float speed = rigidbody.velocity.magnitude; 

/// If using no rigidbody
float speed = (transform.position - this.mLastPosition).magnitude / elapsedTime;
mLastPosition = transform.position;

/// If using CharacterController
Vector3 horizontalVelocity = controller.velocity;
horizontalVelocity = new Vector3(controller.velocity.x, 0, controller.velocity.z);

float horizontalSpeed = horizontalVelocity.magnitude;
float verticalSpeed  = controller.velocity.y;
float overallSpeed = controller.velocity.magnitude;

And to get variables from a parent class, just make those variables static. A prime example of this method is found within my question :