How to implement a dial control that snaps to increments?

Question

How can I implement snapping via code? I have this 2d circle that the players rotate via drag and it works like a rotating dial. The best way to describe what I wanted to achieve is similar to a clock hand snapping to the hour numbers. I'm a total beginner and haven't actually learned anything about quaternions.

This is the my code , im using a raycast to detect if the dial is clicked/dragged.

Vector2 worldPoint = Camera.main.ScreenToWorldPoint(Input.mousePosition);
    RaycastHit2D hit = Physics2D.Raycast(worldPoint, Vector3.forward);

    if (Input.GetMouseButtonDown(0))
    {
        if (hit.collider && hit.collider.GetComponent<Rotate2d>())
        {
            deltaRotation = 0f;
            previousRotation = angleBetweenPoints(transform.position, Camera.main.ScreenToWorldPoint(Input.mousePosition));
        } 
    }

    else if (Input.GetMouseButton(0))
    {
        if (hit.collider && hit.collider.GetComponent<Rotate2d>())
        {
            currentRotation = angleBetweenPoints(transform.position, Camera.main.ScreenToWorldPoint(Input.mousePosition));
            deltaRotation = Mathf.DeltaAngle(currentRotation, previousRotation);

            if (Mathf.Abs(deltaRotation) > deltaLimit)
            {
                deltaRotation = deltaLimit * Mathf.Sign(deltaRotation);
            }

            previousRotation = currentRotation;
            hit.collider.gameObject.transform.Rotate(Vector3.back * Time.deltaTime, deltaRotation);

        }
    }

I forgot to add, here is my angle between points method.

   float angleBetweenPoints(Vector2 position1, Vector2 position2)
{
    Vector2 fromLine = position2 - position1;
    Vector2 toLine = new Vector2(1, 0);

    float angle = Vector2.Angle(fromLine, toLine);

    Vector3 cross = Vector3.Cross(fromLine, toLine);


    // did we wrap around?
    if (cross.z > 0)
    {
        angle = 360f - angle;
    }

    return angle;
}

Answer 1

First, you can simplify your angle method:

public static float DegreesCCWFromRight(Vector2 center, Vector2 pointer) {
    var direction = pointer - center;
    return Mathf.Atan2(direction.y, direction.x) * Mathf.Rad2Deg;
}

Then just round the result to your desired number of increments.

if (hit.collider && hit.collider.GetComponent<Rotate2d>())
{
    Vector2 mouseWorld = Camera.main.ScreenToWorldPoint(Input.mousePosition);
    float angle = DegreesCCWFromRight(transform.position, mouseWorld);

    const float incrementCount = 6;

    angle = Mathf.Round(currentRotation * incrementCount/360) 
                    * 360/incrementCount;

    transform.localEulerAngles = new Vector3(0, 0, angle);
}