Why this "if not Assigned(FList) then" causes an AV??

[garlar27]

Hi,
   I made a class with an TFPList object in it. But when i try to access it I got an Access Violation.
   This is how I use it:

Code: Pascal  [Select][+][-]

1. TMyClass = class(TObject)
2.    ...
3.    FList: TFPList;
4.    ...
5. end;
6.  
7. constructor TMyClass.Create;
8. begin
9.    FLista := nil;
10.    FLista := TFPList.Create;
11. end;
12.  
13. function TMyClass.Add(.....): Integer;
14. begin
15.    if not Assigned(FLista) then begin // Added because the last line caused an AV but now the AV occurs Here!!!
16.       FLista := TFPList.Create;         // Added because the last line caused an AV
17.    end;                                       // Added because the last line caused an AV
18.  
19.    Result := FList.Add(......); // originally this caused the error
20. end;
21.  

Does anybody knows whats wrong?

[theo]

Does anybody knows whats wrong?

You have FList and FLista ?
I can only see declaration of FList.

[garlar27]

Thanks for the quick response!!! But You caught me wen I as trying to remove this thread.

Sorry I've made a mistake I've tried to change FLista to FList to make it more readable and I forgot to change those names  . And other mistake I did in my code does not appears here I called the Add method without creating MyObject but the weird thing is that execution went through many lines of code before reaching the line FList.Add!!!

Code: Pascal  [Select][+][-]

1. TMyClass = class(TObject)  
2.    ...  
3.    FList: TFPList;  
4.    ...  
5. end;  
6.    
7. constructor TMyClass.Create;  
8. begin  
9.    FList := nil;  
10.    FList := TFPList.Create;  
11. end;  
12.    
13. function TMyClass.Add(.....): Integer;  
14. begin  
15.    if not Assigned(FList) then begin // Added because the last line caused an AV but now the AV occurs Here!!!  
16.       FList := TFPList.Create;      // Added because the last line caused an AV  
17.    end;                                // Added because the last line caused an AV  
18.       New(UnDato);
19.       UnDato^.Ubicacion := UnaUbicacion;
20.       UnDato^.Orden := UnOrden;
21.       UnDato^.TipoDato := UnTipoDeDatoFijo;
22.       UnDato^.Texto := UnTexto;//}
23.  
24.    Result := FList.Add(UnDato); // originally this caused the error
25.  

I would have expected the AV a lot earlier: when I call MyObject.Add()

Code: Pascal  [Select][+][-]

1. procedure TForm1.Button1Click(...);
2. begin
3. ...
4. MyObject.Add(.....);
5. ...
6. end;
7.  

This is not the first time it happened to me.

[BlueIcaro]

Hello, did you create your object before use it?

Like this

Var
 MyObject : TMyClass;
Begin
 MyObject := TMyClass.Create; //Create your object called MyObject, class : TMyClass

 MyObject.Add (Somthing); //Then you can use it

/BlueIcaro