# How to create array as class
**URL:** https://forum.castle-engine.io/t/how-to-create-array-as-class/1433
**Category:** Pascal
**Created:** [November 15, 2024, 5:57pm UTC](https://forum.castle-engine.io/t/how-to-create-array-as-class/1433 "2024-11-15T17:57:34Z")
**Posts on this page:** 5
**Page:** 1
### Author:  [@Noscow](https://forum.castle-engine.io/u/Noscow)
#### Post date: [November 15, 2024, 5:57pm UTC](https://forum.castle-engine.io/t/how-to-create-array-as-class/1433/1 "2024-11-15T17:57:34Z")
Good day!
I use `TSptiteBlocksArray` and function `NewSpritesArray` in the next code for ease of working with sprite arrays.
```auto
TViewEnvironmentUnit = class(TCastleView)
type
TSpriteBlocksArray = array of TSpriteBlock;
published
MainMenu : TCastleUserInterface;
QuitButton : TCastleButton;
EnvironmentViewport : TCastleViewport;
Camera : TCastleCamera;
private
FarSpriteBoxes : TSpriteBlocksArray;
CloseSpriteBoxes : TSpriteBlocksArray;
MidSpriteBoxes : TSpriteBlocksArray;
ChrsSpritesBoxes : TSpriteBlocksArray;
InanSpritesBoxes : TSpriteBlocksArray;
***
function NewSpritesArray(Objects : TEssences; Distance : Integer;
Scale : Single; StartTag : Integer): TSpriteBlocksArray;
***
implementation
function TViewenvironmentunit.NewSpritesArray(Objects : TEssences;
Distance : Integer;
Scale : Single;
StartTag : Integer): TSptiteBlocksArray;
var
Sector : Single;
I : Integer;
begin
SetLength(Result, Length(Objects.Essences));
Sector := Pi*2/Length(Result);
for I := 0 to High(Result) do
begin
Result[I] := TSpriteBlock.Create(EnvironmentViewport);
Result[I].PositionBlock(Distance, Sector*I);
Result[I].Scale := Vector3(Scale, Scale, Scale);
Result[I].LoadSprite(Objects.Essences[I].ImageUrl);
Result[I].Sprite.Tag := I + StartTag;
end;
end;
```
But in the function NewSpritesArray compiler indicates `Result` is not exists.
So my questions is:
Is I must create `TSpriteBlocksArray` as class before add sprites
(`Result := TSptiteBlocksArray.Create;`) ? It seems weird, because I haven’t destructor for it.
What is better practice when “array class” is needed?
---
### Author:  [@kagamma](https://forum.castle-engine.io/u/kagamma)
#### Post date: [November 16, 2024, 6:32am UTC](https://forum.castle-engine.io/t/how-to-create-array-as-class/1433/2 "2024-11-16T06:32:31Z")
You can safely ignore it. Managed types like dynamic array are auto initialized, see [Managed types](https://www.freepascal.org/docs-html/ref/refse20.html).
---
### Author:  [@michalis](https://forum.castle-engine.io/u/michalis)
#### Post date: [November 20, 2024, 11:55am UTC](https://forum.castle-engine.io/t/how-to-create-array-as-class/1433/3 "2024-11-20T11:55:33Z")
Alternative answer would be to not use an array 🙂
In all places in CGE, instead of dynamic arrays (`TSpriteBlocksArray = array of TSpriteBlock`) we use generic lists (`TSpriteBlocksArray = specialize TObjectList`) and I’m happy with it – generic classes remain type-safe (you cannot insert wrong class, compiler will not allow it) and have a bit more features (like methods to sort, can also free instances if you pass `true` to constructor, can also easily be changed to `TComponentList<...>` to manage using component-ownership mechanism).
---
### Author:  [@Noscow](https://forum.castle-engine.io/u/Noscow)
#### Post date: [November 22, 2024, 9:43pm UTC](https://forum.castle-engine.io/t/how-to-create-array-as-class/1433/4 "2024-11-22T21:43:20Z")
Thanks, seems like more elegant instrument then native arrays!
As I see, you use generics not from the FGL?
Is there for the compatibility with Delphi?..
I use only Lazarus, so, TFPGObjectList is optimal list generic for me?
---
### Author:  [@michalis](https://forum.castle-engine.io/u/michalis)
#### Post date: [November 23, 2024, 8:42am UTC](https://forum.castle-engine.io/t/how-to-create-array-as-class/1433/5 "2024-11-23T08:42:35Z")
> [@Noscow](#):
>
> As I see, you use generics not from the FGL?
> Is there for the compatibility with Delphi?..
> I use only Lazarus, so, TFPGObjectList is optimal list generic for me?
In general, the `FGL` and `Generics.Collections` units are both reasonable choices IMO to use for generic classes – see [Modern Object Pascal Introduction for Programmers | Castle Game Engine](https://castle-engine.io/modern_pascal#generic-containers-section) , section _" 7.2. Containers (lists, dictionaries) using generics"_.
Some comparison:
- `Generics.Collections` are compatible across FPC and Delphi, this is one of the reasons why we chose them in CGE indeed. `FGL` is only in FPC.
- `Generics.Collections` have out-of-the-box working “comparer” implementations. This meant using them e.g. as lists of records was comfortable out-of-the-box, with FGL we had to define custom operators for comparison. That was a _small_ difference in favor of `Generics.Collections` long time ago for me (though one could argue that FGL, forcing to define the operators, forced the code to be longer but also safer). And this difference doesn’t matter if you only consider lists of objects, i.e. compare `FGL.TFPGObjectList` with `Generics.Collections.TObjectList`.
- `Generics.Collections` in FPC can be annoying as they produce a lot of warnings by default ( [Compiling code using TDictionary from Generics.Collections results in a number of warnings and notes that developer cannot do anything about (#40222) · Issues · FPC / FPC / FPC Source · GitLab](https://gitlab.com/freepascal.org/fpc/source/-/issues/40222) ). If you only compile using CGE build tool/editor, then this doesn’t matter, as we hide these warnings.
All in all, none of the differences matter much, and if your project targets only FPC/Lazarus, then `FGL` is indeed a reasonable choice too. In my personal projects, even if only for FPC/Lazarus, I tend to choose `Generics.Collections` anyway, just because I’m used to some details of it more.