This is a small thing, but it really confused me.
I wanted a particle effect to follow a bone of a SkeletonGraphic. So I created the GameObject, setup my particle effect and dragged it to the right spot in the Canvas's object hierarchy, added the BoneFollowerGraphic script and selected the right bone.
I ran my game, and the script wasn't positioning the effect!
The problem, if you missed it in my step-by-step description: I had created the effect's GameObject outside the canvas and dragged it in, so it didn't get a RectTransform, and BoneFollowerGraphic has this bit in it:
var thisTransform = this.transform as RectTransform;
if (thisTransform == null) return;
I don't think this should fail silently! It's a bit confusing for such an easily made mistake in a legitimate workflow. Either it should AddComponent<RectTransform> (which just replaces Transform with RectTransform) or, if that would have unexpected/unhelpful side effects, print a loud warning in the Console that explains what's going on.
Or even a warning in the BoneFollower Inspector that says "hey, this has a Transform and not a RectTransform, you should add one."
