# How to correctly switch back and forth between scenes?

**URL:** <https://phaser.discourse.group/t/how-to-correctly-switch-back-and-forth-between-scenes/8011>\
**Category:** Phaser 3\
**Created:** [November 3, 2020, 5:17pm UTC](https://phaser.discourse.group/t/how-to-correctly-switch-back-and-forth-between-scenes/8011 "2020-11-03T17:17:14Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![kittykatattack](https://yyz2.discourse-cdn.com/free1/user_avatar/phaser.discourse.group/kittykatattack/32/3888_2.png) [@kittykatattack](https://phaser.discourse.group/u/kittykatattack)\
**Post date:** [November 3, 2020, 5:17pm UTC](https://phaser.discourse.group/t/how-to-correctly-switch-back-and-forth-between-scenes/8011/1 "2020-11-03T17:17:15Z")

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Hi Everyone!

I would love some high level advice on the best way to switch game scenes. I have a level switcher in my game, which allows players to arbitrarily switch back and forth between scenes. (The level switcher is its own Scene, by the way.) Can anyone point me to any existing examples of this? (I haven’t found any in the Phaser 3 examples, and I think I’ve gone through all of them.)

I’ve tried to roll my own version of a scene switcher like this, but switching back to a previously loaded scene (using `start`) throws all kinds of errors for undefined properties. Probably there are some fundamentals that I don’t fully understand. Any advice much appreciated! 😄

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**Author:** ![kittykatattack](https://yyz2.discourse-cdn.com/free1/user_avatar/phaser.discourse.group/kittykatattack/32/3888_2.png) [@kittykatattack](https://phaser.discourse.group/u/kittykatattack)\
**Post date:** [November 4, 2020, 4:48pm UTC](https://phaser.discourse.group/t/how-to-correctly-switch-back-and-forth-between-scenes/8011/2 "2020-11-04T16:48:16Z")

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… after a bit more reading and experimentation:

It _seems_ as if the context from which `start` is called is crucially important. If I’m correct in understanding this, calling `start` from a scene shuts down that scene and starts the new one. ([https://rexrainbow.github.io/phaser3-rex-notes/docs/site/scenemanager/](https://rexrainbow.github.io/phaser3-rex-notes/docs/site/scenemanager/)) So, if that’s correct, a `switchLevel` function like this should work:

```javascript
const switchLevel = (oldScene, newSceneString) => {
  console.log(`From ${oldScene.scene.key} to ${newSceneString}`);
  oldScene.scene.start(newSceneString);
};

```

Which I should be able to call, for example, from a currently active scene like this:

`switchLevel(this, "sceneC")`

This is working in my little test case, but would love know from anyone out there if I’m off track here or there are any gotchas I need to know about… ?

Am I correct in assuming that this:

- Keeps the preloaded assets in the `oldScene` in Phaser’s cache
- Complete destroys the `oldScene` to free up the memory it occupied
- starts the `newScene` , and, if the `newScene` had already been started at some previous time in the game, re-initialises it from scratch?

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**Author:** ![samme](https://yyz2.discourse-cdn.com/free1/user_avatar/phaser.discourse.group/samme/32/5275_2.png) [@samme](https://phaser.discourse.group/u/samme)\
**Post date:** [November 5, 2020, 10:02pm UTC](https://phaser.discourse.group/t/how-to-correctly-switch-back-and-forth-between-scenes/8011/3 "2020-11-05T22:02:57Z")

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`this.scene.start(…)` will always stop the calling scene, yes.

If you’re controlling two scenes from a third scene, you could use instead of `start()`:

```javascript
// From 'c'
this.scene.stop('a').launch('b');

```

Likewise you could use instead of `switch()`:

```javascript
// From 'c'
this.scene.sleep('a').run('b');

```

All caches are global and independent of scene operations.

Stopped scenes aren’t removed, and restarted scenes are just restarted. It’s still the same scene, just in a new phase. Only scene add and remove alter that.

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**Author:** ![kittykatattack](https://yyz2.discourse-cdn.com/free1/user_avatar/phaser.discourse.group/kittykatattack/32/3888_2.png) [@kittykatattack](https://phaser.discourse.group/u/kittykatattack)\
**Post date:** [November 6, 2020, 9:06am UTC](https://phaser.discourse.group/t/how-to-correctly-switch-back-and-forth-between-scenes/8011/4 "2020-11-06T09:06:03Z")

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Thanks so much @samme, that explains a great deal! I haven’t found this documented clearly anywhere else so this is extremely helpful!!

You mentioned that stopped scenes aren’t removed. How does this affect memory? On the game I’m working on there are going to be dozens and dozens of scenes, most of them quite big, so I’d ideally like to completely remove them from memory before switching to a new scene. Should I rather be using `add` and `remove`?

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<div class="post-metadata">

**Author:** ![samme](https://yyz2.discourse-cdn.com/free1/user_avatar/phaser.discourse.group/samme/32/5275_2.png) [@samme](https://phaser.discourse.group/u/samme)\
**Post date:** [November 6, 2020, 5:37pm UTC](https://phaser.discourse.group/t/how-to-correctly-switch-back-and-forth-between-scenes/8011/5 "2020-11-06T17:37:45Z")

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You certainly could use `add` and `remove` instead of `start` and `stop`.

I would guess a stopped scene uses less memory than a running scene, because all of the scene contents are cleared. But more memory than zero.

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<div class="post-metadata">

**Author:** ![kittykatattack](https://yyz2.discourse-cdn.com/free1/user_avatar/phaser.discourse.group/kittykatattack/32/3888_2.png) [@kittykatattack](https://phaser.discourse.group/u/kittykatattack)\
**Post date:** [November 10, 2020, 9:42am UTC](https://phaser.discourse.group/t/how-to-correctly-switch-back-and-forth-between-scenes/8011/6 "2020-11-10T09:42:59Z")

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Thanks @samme, I will try that 🙂