Scripting: make thing repeating

I guess you want to rotate your door by a certain amount of degree over a certain timespan.

Usually you would work with a target rotation you want to reach. This can be "lerped" (linearly interpolated) over time.

You can still use your approach above, but that low WaitForSeconds values might get inaccurate at lower framerates.

This would rotate the object relatively by -90°

 function RotateDoor()
 {
     for (var i = 0; i < 100; i++)
     {
        transform.Rotate(0,-0.9,0);
         yield WaitForSeconds(0.05);
     }
 }

when you call that function the door will rotate -90 in around 5 seconds. WaitForSeconds accumulated in a loop will not be very accurate in the end. Most the time it will take longer than you intended.

A better way is to do something like that:

 function RotateDoor(rotate : Vector3, time : float)
 {
     var initialRot = transform.localRotation;
     var targetRot = transform.localRotation * Quaternion.Euler(rotate);
     var t = 0.0
     while (t < 1.0)
     {
         transform.localRotation = Quaternion.Slerp(initialRot, targetRot, t);
         t += Time.deltaTime / time;
         yield;
     }
 }

This coroutine will perform any relative rotations within the given time.
Some examples:

 // Rotates around y axis by -90° in 2.5 seconds
 RotateDoor(Vector3(0, -90, 0), 2.5);

 // Rotates around y axis by 90° in 1 seconds
 RotateDoor(Vector3(0, 90, 0), 1.0);

 // Rotates around x axis by 45° in half a seconds
 RotateDoor(Vector3(45, 0, 0), 0.5);