We help IT Professionals succeed at work.

SETs in COM

lowlevel
lowlevel asked
on
Medium Priority
203 Views
Last Modified: 2010-04-04
In an OLE automation object, I'd like to include a property that
behaves like a set. But how do I do this? I guess an interfaced enum,
but code like this won't compile:

    options:=[RASEO_TerminalBeforeDial, RASEO_IpHeaderCompression];


options being an interfaced enum, with both values in the "set" actual
values that belong to the enum.

How do I get this to work?
Comment
Watch Question

Commented:
You have to differ between a set and an enumerated type. A set can contain one or more elements, an enumerated type only one.
Normally, you will have to provide an enumeration procedure that steps through the members of the set.
For enumerated types, use the type TOLEEnum to be automation compatible.

Slash/d003303

Commented:
This is the equivalent to a set...check out Windows.pas...This is how Windows does sets...

IDX_Prop1 = 1;  //$00000001   000000001
IDX_Prop2 = 2;  //$00000002   000000010
IDX_Prop3 = 4;  //$00000004   000000100
IDX_Prop4 = 8;  //$00000008   000001000
IDX_Prop5 = 16; //$00000010   000010000
IDX_Prop6 = 32; //$00000020   000100000
IDX_Prop7 = 64; //$00000040   001000000
IDX_Prop8 = 128;//$00000080   010000000
IDX_Prop9 = 256;//$00000100;  100000000

.

Just change everything to a constant...

Rick




Commented:
Here's an example...

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls;
const
IDX_Prop1 = 1;  //$00000001   000000001
IDX_Prop2 = 2;  //$00000002   000000010
IDX_Prop3 = 4;  //$00000004   000000100
IDX_Prop4 = 8;  //$00000008   000001000
IDX_Prop5 = 16; //$00000010   000010000
IDX_Prop6 = 32; //$00000020   000100000
IDX_Prop7 = 64; //$00000040   001000000
IDX_Prop8 = 128;//$00000080   010000000
IDX_Prop9 = 256;//$00000100;  100000000

type
  TEnumProp = (Prop1, Prop2, Prop3, Prop4, Prop5, Prop6, Prop7, Prop8, Prop9);
  TEnumPropSet = set of TEnumProp;
  TForm1 = class(TForm)
    Button1: TButton;
    Label1: TLabel;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
    FEnumPropSet: TEnumPropSet;
  protected
    function GetEnumProp: integer;
  public
    { Public declarations }
    property EnumPropSet: TEnumPropSet read FEnumPropSet write FEnumPropSet;
    property EnumPropValue: integer read GetEnumProp;
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

function TForm1.GetEnumProp: integer;
begin
  result := 0;
  if Prop1 in EnumPropSet then
    Result := IDX_Prop1;
  if Prop2 in EnumPropSet then
    Result := Result + IDX_Prop2;
  if Prop3 in EnumPropSet then
    Result := Result + IDX_Prop3;
  if Prop4 in EnumPropSet then
    Result := Result + IDX_Prop4;
  if Prop5 in EnumPropSet then
    Result := Result + IDX_Prop5;
  if Prop6 in EnumPropSet then
    Result := Result + IDX_Prop6;
  if Prop7 in EnumPropSet then
    Result := Result + IDX_Prop8;
  if Prop8 in EnumPropSet then
    Result := Result + IDX_Prop8;
  if Prop9 in EnumPropSet then
    Result := Result + IDX_Prop9;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
  EnumPropSet := [Prop1, Prop4, Prop5];
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  Label1.Caption := IntToStr(EnumPropValue);
end;

end.

Commented:
opps... forgot the set value...

property EnumPropValue: integer read GetEnumProp write SetEnumProp;

procedure TForm1.SetEnumProp(value: integer);
begin
  FEnumPropSet := [];
  if (Value and IDX_Prop1)=IDX_Prop1  then
    FEnumPropSet:= FEnumPropSet+ [Prop1];
  if Value and IDX_Prop2= IDX_Prop2 then
    FEnumPropSet:= FEnumPropSet+ [Prop2];
  if Value and IDX_Prop3= IDX_Prop3 then
    FEnumPropSet:= FEnumPropSet+ [Prop3];
  if Value and IDX_Prop4= IDX_Prop4 then
    FEnumPropSet:= FEnumPropSet+ [Prop4];
  if Value and IDX_Prop5= IDX_Prop5 then
    FEnumPropSet:= FEnumPropSet+ [Prop5];
  if Value and IDX_Prop6= IDX_Prop6 then
    FEnumPropSet:= FEnumPropSet+ [Prop6];
  if Value and IDX_Prop7= IDX_Prop7 then
    FEnumPropSet:= FEnumPropSet+ [Prop7];
  if Value and IDX_Prop8= IDX_Prop8 then
    FEnumPropSet:= FEnumPropSet+ [Prop8];
  if Value and IDX_Prop9= IDX_Prop9 then
    FEnumPropSet:= FEnumPropSet+ [Prop9];
end;



Commented:
Unlock this solution and get a sample of our free trial.
(No credit card required)
UNLOCK SOLUTION

Commented:
LowLevel...

Have you tried this out???Any problems???Any questions?

Rick

Author

Commented:
I have looked into it, but need more time (very busy here lately)..
I'll try to get it sorted this week.

Author

Commented:
checked it, it works :)

still sucks that it isn't supported by COM, and that there isn't a language feature for it (xEnumValue in xEnum)..

but at least this works :)

Commented:
LowLevel...

aww...but there is...

  if xEnumValue and xEnum(xSet) then

works the same
as

  if xEnumValue in xEnum(xSet) then


if you AND a value against another value it will return true if the value is part of the value...

example

if true and true then  //true
bit pattern:
    01  and  01   =      01

if true and false then //false
bit pattern:
    01  and  00   =      00

if enum2+enum4 in [1,2,4]  then//true
bit pattern:

  001010 and 001011 = true (001010)

So you see Sets are just a more intuitive process when doing Bitwise manipulation...

Rick

Author

Commented:
oh, i knew all that :)

it's just that I'd like a "nice" language feature that allows me to evaluate "if enumvalue in enumtype then blah" as a boolean.
but i guess i can write a function around that...


Unlock the solution to this question.
Thanks for using Experts Exchange.

Please provide your email to receive a sample view!

*This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.

OR

Please enter a first name

Please enter a last name

8+ characters (letters, numbers, and a symbol)

By clicking, you agree to the Terms of Use and Privacy Policy.