How to list objects of a deteminated class?

Question

For example, let’s say I have a class TConfiguracao.

Here constructors and destructors attributes

and in some cultures I create several variables of the type Tconfiguracao

conf1 :TConfiguracao;
conf2 :TConfiguracao;
...

conf1 := TConfiguracao.Create();
conf2 := TConfiguracao.Create();
...

At the close of this form I do:

FreeAndNil(conf1);
FreeAndNil(conf2);

It’s working 100%. What I’d like to know is, is there some way to go through all the objects in that class TConfiguracao and apply a FreeAndNil without knowing exactly how many variables of this type I created? I know there is a way to go through the components of a form in that way

for i := 0 to Form.ComponentCount - 1 do
  begin
    if Form.components[i].classtype is  TEdit then
    begin
      //
    end;
  end;

But objects from other classes I can’t. Is there any way to do this??

Answer 1

Assuming a class and an example type:

TMyClass = class
private
    FIndex : Integer;
public
    //Crio um novo tipo TMyClassArray que representa um array dessa nova classe.
    type TMyClassArray = array of TMyClass;  
    // Crio uma variável de nome Instances que não vai fazer parte dos objetos criados, mas sim da classe. 
    // E por isso deve ser chamada atraves do identificador da classe. 
    class var Instances : TMyClassArray; TMyClass. 
    constructor Create;
    destructor Destroy;
    //Else code...
end;

And his builder:

constructor TMyClass.Create;
begin
    inherited;
    SetLength(Instances, Length(Instances) + 1);
    FI := Length(Instances) - 1;
    Instances[FI] := Self;
    //Else code...
end;

And your destroyer:

destructor TMyClass.Destroy;
var
    I : Integer;
begin
    //Else code...
    Instances[FI] := nil;
    I := FI;
    while(I <= Length(Instances) - 1)do
    beign
        Instances[I] := Instances[I + 1];
        Instances[I].FI := I;
        Inc(I);
    end;
    SetLength(Instances, Length(Instances) - 1);
    inherited;
end;

You can access TMyClass.Instances in your code to get all instances already created.

Note 1: Maybe the destroyer needs better memory handling.

Note 2: The Convention states that Instances be a class property and not class var as I described it only by practicality.

Answer 2

What you can do is use a Tobjectlist.
You must instantiate the Tobjectlist and then you can add your objects in this list through the method Add.
When you destroy Tobjectlist all objects added to it will be destroyed too.
The Ownsobjects property of Tobjectlist must be True(Default) so that it is possible to destroy the objects.
To destroy you can also use Delete, Remove, or Clear method as well.*
Note: You have to add Unit Contnrs in uses.