Convert a Transform to a RectTransform

Question

In my Unity project, I am creating objects dynamically through scripts.

var btnExit = new GameObject("Player " + ID + "'s Exit Button");
btnExit.transform.SetParent(UI.transform);

I need to set the anchors and pivot of the object. I should be able to do that using its RectTransform component, as I do it when I create objects in the scene editor.

myRectTransform.anchorMin = new Vector2(1, 0);
myRectTransform.anchorMax = new Vector2(0, 1);
myRectTransform.pivot = new Vector2(0.5f, 0.5f);

But the object's transform component is not a RectTransform, just the normal Transform. So I can't cast it to use those properties I need.

RectTransform myRectTransform = (RectTransform)btnExit.transform;

So how can I properly use the power of the RectTransform class on an object that I initialise through scripts instead of in the scene editor?

Answer 1

RectTransform rectTransform = transform.GetComponent<RectTransform>();

RectTransform rectTransform = (transform as RectTransform);

RectTransform rectTransform = (RectTransform)transform;

As long as your object has a RectTransform, these are all valid ways to get the RectTransform from the built-in transform reference.

Answer 2

You can directly add a RectTransform component to the gameobject, and the Transform component will change to Rect Transform.

For example:

var btnExit = new GameObject("Player " + ID + "'s Exit Button");
btnExit.AddComponent<RectTransform>();

Then the cast will work:

RectTransform myRectTransform = (RectTransform)btnExit.transform;

P.S.

Without adding the component, the above cast will throw error

InvalidCastException: Cannot cast from source type to destination type.

But with the component added, the cast works fine. Above code is tested in Unity 2018.2.5f1 (64bit).