Originally posted by **ambmcmdmem626** August 5, 2024
**Version: 0.29.3**
## Premise
If an index outside the array is specified for the following two methods,
either `undefined` is returned (`TileMap.getTileByIndex`) or an exception is thrown (`Gif.toSprite`).
\* Content of the Exception: `TypeError: Cannot read properties of undefined (reading 'toSprite')`
- https://github.com/excaliburjs/Excalibur/blob/2e4341f783b0329a960d6f3b2edbafa4d66d0221/src/engine/Resources/Gif.ts#L79-L86
- https://github.com/excaliburjs/Excalibur/blob/2e4341f783b0329a960d6f3b2edbafa4d66d0221/src/engine/TileMap/TileMap.ts#L459-L464
## Main topic
Is there a reason why the return values of these methods are not nullable?
I believe the issue can be addressed by modifying the code as shown below:
- For the comments added to the JSDoc, I referred to `TileMap.getTileByPoint()`( [link](https://github.com/excaliburjs/Excalibur/blob/2e4341f783b0329a960d6f3b2edbafa4d66d0221/src/engine/TileMap/TileMap.ts#L479) ).
- If we decide to implement this change, we should also add corresponding tests, in accordance with the [CONTRIBUTING.md](https://github.com/excaliburjs/Excalibur/blob/main/.github/CONTRIBUTING.md#tests).
## Suggested Code Changes
```
// src/engine/Resources/Gif.ts
/**
* Return a frame of the gif as a sprite by id
* @param id
* returns `null` if no Sprite was found.
*/
public toSprite(id: number = 0): Sprite | null {
const sprite = this._textures[id]?.toSprite() ?? null;
return sprite;
}
```
```
// src/engine/TileMap/TileMap.ts
/**
* Returns the {@apilink Tile} by index (row major order)
* returns `null` if no Tile was found.
*/
public getTileByIndex(index: number): Tile | null {
return this.tiles[index] ?? null;
}
```
Thank you so much for reading this!
eonarheim
commented
1 month ago
Discussed in https://github.com/excaliburjs/Excalibur/discussions/3166