Playing with generics, code to filter items of a given class, using an anonymous procedure. (Already saw FMX.Types TEnumerableFilter used in TListBox, but wanted to do something different).

Playing with generics, code to filter items of a given class, using an anonymous procedure. (Already saw FMX.Types TEnumerableFilter used in TListBox, but wanted to do something different).

For example if you have a Form or Control and you want to do something only with its TButton children controls:

uses MyFilter;

// FireMonkey:

procedure TForm1.CheckBox1Change(Sender: TObject);
begin
  TEnumerableFilter(Children).Find(procedure(Sender:TButton)
     begin
       Sender.Visible:=CheckBox1.IsChecked;
     end);
end;

// VCL:

procedure TForm1.CheckBox1Click(Sender: TObject);
begin
  Find(procedure(Sender:TButton)
     begin
       Sender.Visible:=CheckBox1.Checked;
     end);
end;

(The VCL version is a proper "class helper", as its not possible to create class helpers for generic types).

The code for FireMonkey:

uses
  System.Generics.Collections;

type
  TFindProc=reference to procedure(Sender:F);

  TEnumerableFilter=class(TEnumerable)
  public
    procedure Find(const AProc:TFindProc);
  end;

procedure TEnumerableFilter.Find(const AProc:TFindProc);
var Item : T;
begin
  for Item in Self do
      if Item is T then
         AProc(Item as T);
end;

The code for VCL:

uses VCL.Controls;

type
  TFindProc=reference to procedure(Sender:F);

  TVCLEnumerableFilter=class helper for TWinControl
  public
    procedure Find(const AProc:TFindProc);
  end;

procedure TVCLEnumerableFilter.Find(const AProc:TFindProc);
var i: Integer;
begin
  for i:=0 to ControlCount-1 do
      if Controls[i] is T then
         AProc(Controls[i] as T);
end;