# TUIState is now TCastleView, methods to change the view are now part of Container, new slick UI when opening the project
**URL:** https://forum.castle-engine.io/t/tuistate-is-now-tcastleview-methods-to-change-the-view-are-now-part-of-container-new-slick-ui-when-opening-the-project/703
**Category:** News
**Created:** [December 28, 2022, 6:51am UTC](https://forum.castle-engine.io/t/tuistate-is-now-tcastleview-methods-to-change-the-view-are-now-part-of-container-new-slick-ui-when-opening-the-project/703 "2022-12-28T06:51:01Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@michalis](https://forum.castle-engine.io/u/michalis)
#### Post date: [December 28, 2022, 6:51am UTC](https://forum.castle-engine.io/t/tuistate-is-now-tcastleview-methods-to-change-the-view-are-now-part-of-container-new-slick-ui-when-opening-the-project/703/1 "2022-12-28T06:51:01Z")
| [](https://i0.wp.com/castle-engine.io/wp/wp-content/uploads/2022/12/platformer_map.png?ssl=1 "Platformer game view") |
| [](https://i0.wp.com/castle-engine.io/wp/wp-content/uploads/2022/12/views_in_editor.png?ssl=1 "Editor UI to open existing views") |
We have an important change to one of our most important concepts: _states_ (`TUIState` descendants) are now called _views_ (and descend from `TCastleView`).
It’s a change in terminology, and a change in API. While previously you were changing states using class functions and properties, like `TUIState.Current := Xxx`, now you should use regular container methods, like `Container.View := Xxx`.
Oh, and to this we add a new slick UI when opening the project 🙂
## Why?
It addresses two things:
1. The name _“state”_ was too generic and thus meaningless. Almost every variable and object instance in your application can be called some “state”.
It made sense if you think _“user interface state”_ or _“state of a [state machine](https://en.wikipedia.org/wiki/Finite-state_machine)“_… but the sole word “state” is too generic.
Moreover, `TUIState` class name is not consistent with CGE naming. And `TCastleUIState` or `TCastleUiState` are too convoluted. So for a long time I knew it will have to be renamed to `TCastleState` or `TCastleView`. I finally finished the work to go with `TCastleView`.
_“View”_ doesn’t seem too bad name. It clearly communicates it’s something visual and is a way to “see” CGE stuff. And, _view_ isn’t that often used as a noun, so when someone says _“This view is amazing”_ you can fairly safely assume they talk about `TCastleView` (assuming you’re in the middle of CGE manual, not on a hiking trip 🙂 ).
It is consistent e.g. with [React view](https://reactnative.dev/docs/view).
2. The way we changed states, using `TUIState` class methods/properties, could be improved to use simple methods on `Container`.
## Upgrading
This change is _100% backward-compatible_. The old code will continue to work, though we advise you to upgrade to new names and container methods/properties.
In total, the upgrade path in typical applications is rather straightforward, although it will require to do a lot of replacements (I recommend to commit everything to your version control before doing the upgrade, and then have a nice diff to audit with state-\>view upgrade):
1. Rename `TUIState` -\> `TCastleView`.
2. Remove `CastleUIState` unit from your uses clause. Make sure unit `CastleUIControls` is there (it likely is there already).
3. Change in ApplicationInitialize:
4. Change in various states (views):
5. Optionally, as a final touch: rename your units and designs.
## New editor UI when opening new project
This is accompanied by a cool upgrade to our CGE editor UI. It happened because of independent reasons (I did UX testing on a live human at Christmas :), and came back with lots of nice conclusions) but it is nicely connected with the whole _views_ terminology.
Now, when opening any project, you will be greeted with a UI to
- compile and run / stop the project
- create a new view (Pascal unit and design)
- open an existing view
This UI emphasizes your most recommended actions after opening the project.
## Docs
Our documentation, including important chapters about [view events](https://castle-engine.io/view_events) and [managing views](https://castle-engine.io/views), has been upgraded to new terminology.
Our examples are also fully upgraded now to use _view_ terminology everywhere.
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### Author:  [@Carring](https://forum.castle-engine.io/u/Carring)
#### Post date: [January 23, 2023, 6:56am UTC](https://forum.castle-engine.io/t/tuistate-is-now-tcastleview-methods-to-change-the-view-are-now-part-of-container-new-slick-ui-when-opening-the-project/703/2 "2023-01-23T06:56:18Z")
I have followed the upgrading changes but get this error?
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### Author:  [@michalis](https://forum.castle-engine.io/u/michalis)
#### Post date: [January 23, 2023, 11:54am UTC](https://forum.castle-engine.io/t/tuistate-is-now-tcastleview-methods-to-change-the-view-are-now-part-of-container-new-slick-ui-when-opening-the-project/703/3 "2023-01-23T11:54:11Z")
Look at the type of your `StatePlay` variable (it is in `GameStatePlay` unit, you can just ctrl + click on it in Lazarus to jump to declaration). It likely has a type `TStatePlay`, so here you should create `StatePlay := TStatePlay.Create...` .
Also, `TCastleView` is in `CastleUIControls` . Which you can find by searching for it in API docs, [Castle Game Engine: CastleUIControls: Class TCastleView](https://castle-engine.io/apidoc/html/CastleUIControls.TCastleView.html) . But, you don’t want to create just `TCastleView` there.
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### Author:  [@Carring](https://forum.castle-engine.io/u/Carring)
#### Post date: [January 23, 2023, 12:37pm UTC](https://forum.castle-engine.io/t/tuistate-is-now-tcastleview-methods-to-change-the-view-are-now-part-of-container-new-slick-ui-when-opening-the-project/703/4 "2023-01-23T12:37:29Z")
I now have StatePlay := TCastleViewPlay.Create(Application) in TStateMenu but now I get an error message I did not have before when using TStatePlay?
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### Author:  [@michalis](https://forum.castle-engine.io/u/michalis)
#### Post date: [January 23, 2023, 2:44pm UTC](https://forum.castle-engine.io/t/tuistate-is-now-tcastleview-methods-to-change-the-view-are-now-part-of-container-new-slick-ui-when-opening-the-project/703/5 "2023-01-23T14:44:33Z")
Hm, this error message seems unrelated to TUIState → TCastleView rename, and indicates some problem you had before or that you did something weird at conversion. I’m afraid I cannot tell where’s the problem looking at the screenshot.
Please submit a testcase to reproduce the problem, preferably a small testcase.
If you have a version control (as I recommended in [TUIState is now TCastleView, methods to change the view are now part of Container, new slick UI when opening the project – Castle Game Engine](https://castle-engine.io/wp/2022/12/28/tuistate-is-now-tcastleview-methods-to-change-the-view-are-now-part-of-container-new-slick-ui-when-opening-the-project/) as I recommend in general – use version control) then please look at your changes, and see whether they make sense, if you didn’t touch anything unusual.