I need to create some databases at runtime which use same event handling code as a component created at design time.

Is there some way to set the event handling property of a component at runtime?

2011/1/4 Frank Church :

Is there some way to set the event handling property of a component at runtime?

SomeComponent.OnSomeEvent := @YourEventHandler;

Hi Frank,

Date: Tue, 4 Jan 2011 17:56:54 +0000
From:
To:
Subject: [Lazarus] How do you set an event at runtime?

I need to create some databases at runtime which use same event handling code as a component created at design time. Is there some way to set the event handling property of a component at runtime?

I am not sure about databases but with a TMainMenu's TMenuItems component, in Delphi 7 I do this:

This code is all ten+ years old !
// modified by P.Williams 28 Sept 2000
uses collect_two_wd_cmd;
procedure TeditForm.CommandHandler(Sender: TObject);
begin
  // do whatever you like
end;
procedure TeditForm.define_commands_menu;
var
  j : integer;
  amenuitem : tmenuitem;
begin
  commands1.clear;
  amenuitem := tmenuitem.create( self );
  amenuitem.caption := '<New 2 Word Command>';
  amenuitem.OnClick := CommandHandler;
  commands1.add( amenuitem );
  for j := 0 to command.count - 1 do
    if command.items[ j ].command_name  '' then
    begin
      amenuitem := tmenuitem.create( self );
      amenuitem.caption := command.items[ j ].command_name;
      amenuitem.OnClick := CommandHandler;
      commands1.add( amenuitem );
    end;

end; { define_commands_menu }

{---------------------------------------------------------}

// Collect_two_wd_cmd.PAS -- defines the custom components TNodeList and TNode, based
//                on the Delphi components TCollection and TCollectionItem,
//                respectively. Author: Steve Koterski; 9/4/97.
//
// modified by P.Williams 11 Oct 2000
unit collect_two_wd_cmd;
interface

uses

  Windows, SysUtils, Classes, collect2;
  // collect2 is one of my own components
type
  string20 = string[20];
  TNode = class(TCollectionItem)
  private
    // this is the private data variables
    fcommand_name: string20;
    fcommand_effect_table: t2_wd_cmd_sub_nodelist;
  protected
  public
  published
    procedure Assign(Source: TPersistent); override;
    // this is the published data variables
    property command_name: string20 read fcommand_name write fcommand_name;
    property command_effect_table: t2_wd_cmd_sub_nodelist
      read fcommand_effect_table write fcommand_effect_table;
  end;
  T2_wd_cmd_NodeList = class(TCollection)
  private
    FOwner: TPersistent;
    function GetItem(Index: Integer): TNode;
    procedure SetItem(Index: Integer; Value: TNode);
  protected
    function GetOwner: TPersistent; override;
  public
    constructor Create(Owner: TPersistent);
//    destructor Destroy; override;
    procedure Add(command_name: string20; command_effect_table: t2_wd_cmd_sub_nodelist);
    property Items[Index: Integer]: TNode read GetItem write SetItem; default;
  published
  end;
implementation

{TNode}

procedure TNode.Assign(Source: TPersistent);
begin
  command_name := TNode(Source).command_name;
  command_effect_table := TNode(Source).command_effect_table;
end;

{TNodeList}

constructor T2_wd_cmd_NodeList.Create(Owner: TPersistent);
begin
  FOwner := Owner;
  inherited Create(TNode);
end;

{

destructor T2_wd_cmd_NodeList.Destroy;
var
  i: Integer;
begin
  for i := 0 to Count - 1 do
    if Assigned(Items[i]) then
      Items[i].Free;
  Inherited;
end;

}

function T2_wd_cmd_NodeList.GetItem(Index: Integer): TNode;
begin
  Result := TNode(inherited GetItem(Index));
end;
procedure T2_wd_cmd_NodeList.SetItem(Index: Integer; Value: TNode);
begin
  inherited SetItem(Index, TCollectionItem(Value));
end;
procedure T2_wd_cmd_NodeList.Add(command_name: string20;
  command_effect_table: t2_wd_cmd_sub_nodelist);
var
  n: TNode;
begin
  n := TNode(inherited Add);
  n.command_name := command_name;
  n.command_effect_table := command_effect_table;
end;
function T2_wd_cmd_NodeList.GetOwner: TPersistent;
begin
  Result := FOwner;
end;
end.
// COLLECT.PAS -- defines the custom components TNodeList and TNode, based
//                on the Delphi components TCollection and TCollectionItem,
//                respectively. Author: Steve Koterski; 9/4/97.
//
// modified by P.Williams 28 Sept 2000
unit collect2;
interface

uses

  Windows, SysUtils, Classes;
type
  TNode = class(TCollectionItem)
  private
    // this is the private data variables
    fobject_no,
      feffect_code,
      fconditional_on: integer;
  protected
  public
  published
    procedure Assign(Source: TPersistent); override;
    // this is the published data variables
    property object_no: integer read fobject_no write fobject_no;
    property effect_code: integer read feffect_code write feffect_code;
    property conditional_on: integer read fconditional_on write fconditional_on;
  end;
  T2_wd_cmd_sub_NodeList = class(TCollection)
  private
    FOwner: TPersistent;
    function GetItem(Index: Integer): TNode;
    procedure SetItem(Index: Integer; Value: TNode);
  protected
    function GetOwner: TPersistent; override;
  public
    constructor Create(Owner: TPersistent);
//    destructor Destroy; override;
    procedure Add(object_no, effect_code, conditional_on: integer);
    property Items[Index: Integer]: TNode read GetItem write SetItem; default;
  published
  end;
implementation

{TNode}

procedure TNode.Assign(Source: TPersistent);
begin
  object_no := TNode(Source).object_no;
  effect_code := TNode(Source).effect_code;
  conditional_on := TNode(Source).conditional_on;
end;

{TNodeList}

constructor T2_wd_cmd_sub_NodeList.Create(Owner: TPersistent);
begin
  FOwner := Owner;
  inherited Create(TNode);
end;

{

destructor T2_wd_cmd_sub_NodeList.Destroy;
var
  i: Integer;
begin
  for i := 0 to Count - 1 do
    if Assigned(Items[i]) then
      Items[i].Free;
  Inherited;
end;

}

function T2_wd_cmd_sub_NodeList.GetItem(Index: Integer): TNode;
begin
  Result := TNode(inherited GetItem(Index));
end;
procedure T2_wd_cmd_sub_NodeList.SetItem(Index: Integer; Value: TNode);
begin
  inherited SetItem(Index, TCollectionItem(Value));
end;
procedure T2_wd_cmd_sub_NodeList.Add(object_no, effect_code, conditional_on: integer);
var
  n: TNode;
begin
  n := TNode(inherited Add);
  n.object_no := object_no;
  n.effect_code := effect_code;
  n.conditional_on := conditional_on;
end;
function T2_wd_cmd_sub_NodeList.GetOwner: TPersistent;
begin
  Result := FOwner;
end;
end.

pew