Restarting after Game Over - Player Error

I am trying to restart my game after the player has died for the first time. The flow is:

Bootstrap >> Main Menu >> Game Level >>
Player Dies >> Game Over Menu >> Main Menu >> Game Level

The following error is thrown in the last step, going from the Main Menu back to the Game Level (after the player has died for the first time):

Code (JavaScript):

1.  
2. ut.World.hasComponent(): Invalid entity [31:1] (DELETED) when attempting to query existence of component game.PlayerTag (Component ID 61)
3. Callstack:
4.   World.hasComponentRaw (http://localhost:19050/runtime.js:127248:19)
5.   World.hasComponent (http://localhost:19050/runtime.js:127602:16)
6.   World.getOrAddComponentData (http://localhost:19050/runtime.js:127835:13)
7.  

This sounds like there is a problem with the player entity or the player tag component.

What I do not understand is that this only happens after the game has been played once. It works fine when going from Bootstrap to Main Menu to Game Level. The error only arises after the player has died for the first time.

What can I do to solve this?

---

Here is the code I think may be relevant:

Code (JavaScript):

1. // GameService
2. static launchGameOver( world: ut.World, gameConfig: game.GameConfig ) {
3.          
4.     // instantiate the game-over menu
5.     ut.EntityGroup.instantiate( world, this.gameOverGroupName );
6.  
7.     // stop all game-level entities
8.     this.stopGameLevel( world );
9.  
10.     // set the game-state to game-over
11.     gameConfig.gameState = game.GameState.GameOver;
12. };
13.  
14. // GameManagerSystem
15. case game.GameState.GameOver:
16. {
17.     // if the player pressed the primary mouse-button
18.     if( ut.Runtime.Input.getMouseButtonDown( 0 ) ) {
19.      
20.         // reinitialises the app and return to the main-menu
21.         game.GameService.reinitialiseApp( this.world, gameConfig );
22.     }
23. }
24.  
25. // GameService
26. static reinitialiseApp( world: ut.World, gameConfig: game.GameConfig ) {
27.  
28.     // set the game-state to initialise
29.     gameConfig.gameState = game.GameState.Initialise;
30. }
31.  
32. // GameManagerSystem
33. case game.GameState.Initialise:
34. {
35.     // initialise the app and launch the main-menu
36.     game.GameService.initialiseAppAndLaunchMainMenu( this.world, gameConfig );
37. }
38. break;
39.  
40. // GameService
41. static initialiseAppAndLaunchMainMenu( world: ut.World, gameConfig: game.GameConfig ) {
42.  
43.     // reset the app back to its original state
44.     this.resetApp( world, gameConfig );
45.  
46.     // instantiate the main-menu-group
47.     ut.EntityGroup.instantiate( world, this.mainMenuGroupName );
48.  
49.     // set the game-state to main-menu
50.     gameConfig.gameState = game.GameState.MainMenu;
51. }
52.  
53. // GameService
54. static resetApp( world: ut.World, gameConfig: game.GameConfig ) {
55.  
56.     // clear all entities from the game that was just played (player died)
57.     ut.EntityGroup.destroyAll( world, this.gameLevelGroupName );
58.     ut.EntityGroup.destroyAll( world, this.gameOverGroupName );
59.     ut.EntityGroup.destroyAll( world, this.enemyGroupName );
60.     ut.EntityGroup.destroyAll( world, this.enemyLaserGroupName );
61.     ut.EntityGroup.destroyAll( world, this.explosionGroupName );
62.     ut.EntityGroup.destroyAll( world, this.playerLaserGroupName );
63. }
64.  
65. // GameManagerSystem
66. case game.GameState.MainMenu:
67. {
68.     // if the player pressed the primary mouse-button
69.     if( ut.Runtime.Input.getMouseButtonDown( 0 ) ) {
70.      
71.         // launch the game-level
72.         game.GameService.launchGameLevel( this.world, gameConfig );
73.     }
74. }
75.  
76. // GameService
77. static launchGameLevel( world: ut.World, gameConfig: game.GameConfig ) {
78.  
79.     // clear the main-menu entity
80.     ut.EntityGroup.destroyAll( world, this.mainMenuGroupName );
81.  
82.     // instantiate the game-level-group
83.     // NOTE: the player is part of this group
84.     ut.EntityGroup.instantiate( world, this.gameLevelGroupName );
85.  
86.     // set the game-state to play
87.     gameConfig.gameState = game.GameState.Play;
88. }

 

It appears the problem was caused by the way in which I get the player.

Changing

Code (JavaScript):

1. if( this.player == null ) {
2.  
3.     // for each entity that has the player-tag component
4.     this.world.forEach(
5.         [ ut.Entity, game.PlayerTag ],
6.         ( entity, playerTag ) => {
7.        
8.             // store a reference to the player-entity
9.             this.player = new ut.Entity( entity.index, entity.version );
10.         }
11.     );
12. }

to

Code (JavaScript):

1. this.player = this.world.getEntityByName( "Player" );  

in all my scripts appears to solve the problem.

I have multiple scripts that need to get a reference to the player entity, what is the best way to do this?

 

The error you mentioned occurs whenever you do a .hasComponent() on an entity which has been deleted (for example by ut.EntityGroup.destroyAll() on the group which contains your player). I think the reason why this is occuring in your case is because you used to copy your player's entity into a variable. After the player-entity has been destroyed, your variable still contains the player's index and version, and you probably tried using a .hasComponent() on this variable, containing your deleted entity.

A thing you could do to pinpoint your exact error location would be to go into your browser console an click the little arrow at the top left corner of the error. Then you can follow the stacktrace towards the first system you encounter which belongs to you, and click on it to let the browser take you to the exact line of the error:


I'm not sure how exactly you are using your player-entity in your scripts, but using this.world.getEntityByName("Player"), is normally not recommended, especially when using it quite often. Normally (but again, I don't know your code structure), you would execute the code that you would like to execute on the player-entity within the this.world.forEach(). This way, you do not need to save the reference of the player, making your code more fail-safe.

 

Btw, Zionisias, how you're working with objects on the scene that must be presented in the single instance only (like a "Player")?

For example, case:
"Check if the [current] player has more than 300 points".

 

Even if there is only 1 player, I still use a .forEach(). How I set up my code, I know that there will only be a single player at a given time, so this normally does not cause any issues.

For example: If you would indeed like to check if the score of the player is greater than 300, I would just do:

Code (CSharp):

1. this.world.forEach([ut.Entity, game.PlayerTag], (entity, playerComp) => {
2.       if(playerComp.Score > 300){
3.             //Execute code
4.       }
5. });