One frequent question since Delphi 6 shipped has concerned the disappearance of Proxies.pas from the source.

This change is part of a larger trend.

Borland chose not to ship DsgnIntf.dcu with Delphi 5, apparently to force compliance with the Delphi and C++Builder license agreements. The design-time code had been inadvertently used at runtime by many components. In some ways Borland encouraged this behavior: If you use the new component wizard you will see that this wizard creates only one unit, putting both the component skeleton code (runtime) and the Register procedure (design-time) in the same unit.

With Delphi 6, Borland has taken the next step. Not only was DsgnIntf replaced with DesignIntf, but the property editors were also pulled out into DesignEditors, DesignMenus, DesignWindows and other design-time files. DesignEditors in particular uses another IDE file named Proxies. (The Proxies code resides in DesignIDE.bpl.) Needless to say, these changes can result in errors at compile time.

If your code is already segregated in terms of runtime versus design-time then the fix is very simple. Open up your design-time package, select the requires folder and hit the Add button. Type designide.dcp and hit OK. Recompile your package and the error should go away.

But how can this problem be fixed when design-time and runtime code has been mixed together? DesignIDE.bpl is not a redistributable package in Delphi. So even in situations where the "design-time only" package has the component's runtime code and only the component dcu is used, there can still be a problem.

In 99.99% of the cases this is actually very easy to fix. Your runtime code isn't actually using the design-time code; things just are not properly segregated. The segregation lines are fairly simple, however.

The design-time package should include:

1. All registration statements.
2. All property editors.
3. All Component editors.
4. Should require DesignIDE and each runtime package that holds the components themselves.

The runtime package should include:

1. The components themselves only.
2. Optionally, any forms the editors may use IF the component can call the form itself at runtime

The only place where there is a little confusion is if the property/component editor uses a form. If that form is available at runtime to the component, it belongs in the runtime package. If it is only available at design-time, it goes in the design-time package. A very common misperception is that the form itself is the editor, but it is not. It is the component editor that calls the form that is the design-time editor.

You should get in the habit of always separating your components into two packages even if you only statically link your application, because mixing design-time and runtime code leads to code bloat. Your design-time code can't be executed in the runtime, but the linker doesn't know that so it links it in anyway. (This is why DsgnIntf is trying to get linked in.)

Let's walk though a very simple component to see how to break the design-time code from the runtime:

{ TMixedComponent }
TMixedComponent = class(TComponent)
  private
    FFileName: String;
  published
    property  FileName : String read FFileName write FFileName;
    { Published declarations }
  end;
  { TMixedFileNameProperty }
  TMixedFileNameProperty = class(TPropertyEditor)
    function    AllEqual: boolean; override;
    procedure   Edit; override;
    function    GetAttributes: TPropertyAttributes; override;
    function    GetValue: string; override;
    procedure   SetValue (const  Value: string); override;
  end;
procedure  Register;

implementation

procedure  Register;
begin
  RegisterPropertyEditor(TypeInfo(string), TMixedComponent, 'FileName', TMixedFileNameProperty);
  RegisterComponents('Samples', [TMixedComponent]);
end;

function  TMixedFileNameProperty.AllEqual: boolean;
var
  FirstVal: string;
  i: Integer;
begin
  FirstVal := GetStrValue;
  Result := True;
  i := 1;
  while  Result and  (i < PropCount) do
  begin
    Result := Result and  (GetStrValueAt(i) = FirstVal);
    Inc(i);
  end;
end;

procedure  TMixedFileNameProperty.Edit;
var
  Dlg: TOpenDialog;
begin
  Dlg := TOpenDialog.Create(Application);
  try
    with  Dlg do
    begin
      Title := 'File for ' + TComponent(GetComponent(0)).Name;
      FileName:= Value;
      if  Execute then  Value := FileName;
    end;
  finally
    FreeAndNil(Dlg);
  end
end;

function  TMixedFileNameProperty.GetAttributes: TPropertyAttributes;
begin
  Result := [paDialog]
end;

function  TMixedFileNameProperty.GetValue: string;
begin
  Result := GetStrValue;
end;

procedure  TMixedFileNameProperty.SetValue(const  Value: string);
begin
  SetStrValue(Value);
end;

end.

The easiest way to segregate the design-time code from runtime code is to take all the code that requires DesignIntf and DesignEditors and put it in its own unit. That unit will need to use the component's unit. The component itself does not have need to know about the IDE editors that will work with it. So for a start, remove the design-time units DesignIntf and DesignEditors from the uses clause component unit and let the compiler/linker tell you which classes need to be moved into their own unit:

• [Error] MixedComponent.pas(23): Undeclared identifier: 'TPropertyEditor'
• [Error] MixedComponent.pas(23): Class type required
• [Error] MixedComponent.pas(24): Method 'AllEqual' not found in base class
• [Error] MixedComponent.pas(25): Method 'Edit' not found in base class
• [Error] MixedComponent.pas(26): Undeclared identifier: 'TPropertyAttributes'
• [Error] MixedComponent.pas(27): Method 'GetValue' not found in base class
• [Error] MixedComponent.pas(28): Method 'SetValue' not found in base class
• [Error] MixedComponent.pas(35): Undeclared identifier: 'RegisterPropertyEditor'
• [Error] MixedComponent.pas(35): Undeclared identifier: 'TMixedFile'
• [Error] MixedComponent.pas(46): Undeclared identifier: 'GetStrValue'
• [Error] MixedComponent.pas(49): Undeclared identifier: 'PropCount'
• [Error] MixedComponent.pas(51): Undeclared identifier: 'GetStrValueAt'
• [Error] MixedComponent.pas(51): Operator not applicable to this operand type
• [Error] MixedComponent.pas(64): Undeclared identifier: 'GetComponent'
• [Error] MixedComponent.pas(65): Undeclared identifier: 'Value'
• [Error] MixedComponent.pas(75): Undeclared identifier: 'paDialog'
• [Error] MixedComponent.pas(80): Undeclared identifier: 'GetStrValue'
• [Error] MixedComponent.pas(85): Undeclared identifier: 'SetStrValue'
• [Fatal Error] JOComponents.dpk(33): Could not compile used unit 'MixedComponent.pas'

The next step is to create a new unit to hold the design-time code. Name it something like MixedComponentReg. Move the Register procedure over to that unit. Now start going through the error messages and start evaluating them. The first error, [Error] MixedComponent.pas(23): Undeclared identifier: 'TPropertyEditor', indicates that the whole class inherits from something in one of the design-time units we removed. This is a clear indication that this is only design-time code and the whole class needs to be moved over to the newly created unit.

At this point the runtime package now compiles cleanly (if not, keep pulling design-time code out until it compiles cleanly without errors). Now there is no need for Proxies.pas or any other design-time units for the component to work in your application at runtime. The runtime component unit is much simplified. It looks like this:

unit MixedComponent;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs;

type
  { TMixedComponent }
  TMixedComponent = class(TComponent)
  private
    FFileName: String;
  published
    property FileName : String read FFileName write FFileName;
    { Published declarations }
  end;

implementation

end.

The final step is to get the component and its property editors compiled into a design-time package and installed into the IDE.

Create a new package by doing File | New | Other and select package. Bring up the packages options and select design-time only. Give a descriptive name in the Description field. Select the Requires folder and hit the Add button. In the Requires Package edit box type Designide.dcp and hit OK. Also add the dcp for the runtime package that the component resides in. In this case it was put it in JOComponents.dpk, so JOComponents.dcp is added to the requires section. The requires section has three items: JOComponents, designide and rtl. Finally, select the Contains folder and add MixedComponentReg.pas to the package.

We're almost done!

Open up MixedComponentReg.pas to add a couple of units in the uses section. Which section depends on whether your component or property editor uses the component in its declaration (more complicated editors sometimes need knowledge of the component). If it does, then add it to the Interface uses clause. If not, put it in the implementation uses. In our example we don't need the information so MixedComponent goes in the implementation uses clause. DesignIntf and DesignEditors belong in the Interface uses. SysUtils, Forms, Dialogs, and Classes are all used internally in different ways in the property editor, so they belong in the implementation section. The final MixedComponentReg looks like this:

unit MixedComponentReg;

interface

uses DesignIntf, DesignEditors;

type
  { TMixedFileNameProperty }
  TMixedFileNameProperty = class(TPropertyEditor)
    function  AllEqual: boolean; override;
    procedure Edit; override;
    function  GetAttributes: TPropertyAttributes; override;
    function  GetValue: string; override;
    procedure SetValue (const Value: string); override;
  end;

procedure Register;

implementation

uses MixedComponent, SysUtils, Forms, Dialogs, Classes;

procedure Register;
begin
  RegisterPropertyEditor(TypeInfo(string), TMixedComponent, 'FileName', TMixedFileNameProperty);
  RegisterComponents('Samples', [TMixedComponent]);
end;

function TMixedFileNameProperty.AllEqual: boolean;
var
  FirstVal: string;
  i: Integer;
begin
  FirstVal := GetStrValue;
  Result := True;
  i := 1;
  while Result and (i < PropCount) do
  begin
    Result := Result and (GetStrValueAt(i) = FirstVal);
    Inc(i);
  end;
end;

procedure TMixedFileNameProperty.Edit;
var
  Dlg: TOpenDialog;
begin
  Dlg := TOpenDialog.Create(Application);
  try
    with Dlg do
    begin
      Title := 'File for ' + TComponent(GetComponent(0)).Name;
      FileName:= Value;
      if Execute then Value := FileName;
    end;
  finally
    FreeAndNil(Dlg);
  end
end;

function TMixedFileNameProperty.GetAttributes: TPropertyAttributes;
begin
  Result := [paDialog]
end;

function TMixedFileNameProperty.GetValue: string;
begin
  Result := GetStrValue;
end;

procedure TMixedFileNameProperty.SetValue(const Value: string);
begin
  SetStrValue(Value);
end;

end.

All that is left is to compile and install the design-time package.

The runtime code is now completely segregated from the design-time code.

While this is a fairly simple example, the only time it gets a little more complicated is when the property editor uses a form to retrieve the data, and that form is also available at runtime. In those cases the form stays in the runtime package, and the design-time property editor will call that form from the runtime package.

If you get in the habit of always having a runtime package for the components and a design-time package for the registration and editors, you won't have any more problems, even if you only intend to statically link in the DCUs.

By Jeff Overcash (TeamB).