How do I use coroutines to animate properly?

Question

I have a coroutine, which I called from the Update() method on every click.

First, I call AddTrunk() to add to my trunkList, then I use my coroutine to move the animation for 0.3 seconds. After 0.3 seconds, it calls Destroy(), and then it changes transform.position. However, before completing the animation, it runs transform.position; it first my tree down first, and then does the animation.

---

This is where I call my coroutine:

void Update () 
{
    if (Input.GetMouseButtonDown (0)) 
    {
        AddTrunk ();

        if (!isRunning) 
        {
            StartCoroutine (BranchOutAnimation ());
        }
    }
}

Here is the coroutine BranchOutAnimation():

IEnumerator BranchOutAnimation()
{
    while (true) 
    {
        isRunning = true;
        iTween.MoveTo (trunkList[index], 
            new Vector3 (trunkList[index].transform.position.x 
            - 5f, trunkList[index].transform.position.y, 
            trunkList [index].transform.position.z), 0.3f);
        yield return new WaitForSeconds (0.3f);

        Destroy (trunkList [index]);
        trunkList.RemoveAt (index);
        transform.position = new Vector3 (transform.position.x, transform.position.y 
            - treeHeight, transform.position.z);
        isRunning = false;
        yield break;
    }
}

---

What am I doing wrong?

Answer 1

Calling yield break breaks the coroutine and the while loop in it won't start over again. The while loop goes through only once after waiting for 0.3 seconds. Use the yield break only when you want to break out from the coroutine. If you want the while loop to go through multiple times, try yield return null; which will just make the coroutine to wait for one frame.

If you actually want to run the whole code block only once, just remove the while loop as it would behave exactly the same.

Based on your code I'm guessing/assuming you want to grow the tree until there are no more trunks in the list, and finally just remove the whole tree. Here's some untested code to help you out:

IEnumerator BranchOutAnimation()
{
    // Make sure we are running only one coroutine
    if(isRunning)
        yield break;

    isRunning = true;

    // Which index did we start from?
    int trunkIndex = index;

    // Just make the animation interval configurable for easier modification later
    const float animationInterval = 0.3f;

    // Loop until instructed otherwise
    while (true) 
    {
        // Do some nice animation
        iTween.MoveTo (trunkList[trunkIndex], new Vector3 (trunkList[trunkIndex].transform.position.x - 5f, trunkList[trunkIndex].transform.position.y, trunkList [trunkIndex].transform.position.z), animationInterval);

        // Make the coroutine wait for a moment
        yield return new WaitForSeconds (animationInterval);

        // Increase index of the animation
        trunkIndex++;

        // Check if we have reached the last index
        if(trunkIndex == trunkList.Count)
        {
            // Break the while loop, NOT the coroutine
            break;
        }
    }

    // Finally just remove the whole tree
    for(int i = trunkList.Count - 1; i >= 0 ; i--)
    {
        Destroy (trunkList [i]);
        trunkList.RemoveAt (i);
        transform.position = new Vector3 (transform.position.x, transform.position.y - treeHeight, transform.position.z);
    }

    isRunning = false;
}