Why am I getting this error in Unity3D?

Question

This is the error I am getting:

Assets/Scripts/CameraScript.cs(60,39): error CS1612: Cannot modify a value type return value of `UnityEngine.Transform.position'. Consider storing the value in a temporary variable

This is my code:

void  Start (){
        thisTransform = transform;

        // Disable screen dimming
        Screen.sleepTimeout = 0;
    }

    void  Update (){
        //Reset playerscore 
        playerScore = settings.playerScore;

        //Smooth follow player character
        if  (target.position.y > thisTransform.position.y)  {           
            thisTransform.position.y = Mathf.SmoothDamp( thisTransform.position.y, 
                                                        target.position.y, ref velocity.y, smoothTime);
        }
    }

Answer 1

You can't set the thisTransform.position.y value alone. Set the thisTransform.position instead.

For example:

if  (target.position.y > thisTransform.position.y)  {           
  thisTransform.position = new Vector3(thisTransform.position.x, 
                                       Mathf.SmoothDamp( thisTransform.position.y, target.position.y, ref velocity.y, smoothTime), 
                                       thisTransform.position.z);
}

Answer 2

Transform.position.y is read-only in C#, so in order to modify it you'll need to store the value of Transform.position to a temporary variable first, change the value from that variable, then assign it back to Transform.position:

Vector3 temp = thisTransform.position;
temp.y = Mathf.SmoothDamp( temp.y, target.position.y, ref velocity.y, smoothTime);
thisTransform.position = temp;