HowToDoThings.com Delphi

Purchase order lines

Peter5 — Tue, 23 Aug 2005 05:23:00 -0500

When creating an association in ECO you are not guaranteed the order in which the objects at the end of the association will be presented. For this reason ECO provides a Boolean "ordered" property on association ends.

When you set Ordered = True in your model and then generate your database, ECO will create an additional column in your database identifying the sequence of the objects.

I have just been creating SalesInvoice / SalesInvoiceLine classes and chose to have an ordered association, basically because it is standard industry practise to identify each line of an Invoice/Order with a sequencial number, making it easily identifyable when discussing it.

It would have been nice if I could have used an OCL derived attribute with an expression similar to this:

this.SalesInvoice.lines->indexOf(self)

Application.ProcessMessages replacement

Mon, 15 Aug 2005 06:46:00 -0500

Not only is Application.ProcessMessages quite long to type, often extra functionality needs to be called when its used. To this end I have created two basic wrappers which can be used in its place:

...

procedure ProcessMsg(); overload;
procedure ProcessMsg(const SleepFor: Word); overload;

implementation

procedure ProcessMsg();
begin
ProcessMsg(0);
end;

procedure ProcessMsg(const SleepFor: Word); overload;
begin
Application.ProcessMessages();
Sleep(SleepFor);
end;

...

Now instead of writing Application.ProcessMessages(); in your code you can write ProcessMsg(); instead. And in the future you can extend what happens around Application.ProcessMessages calls without visiting lots of different areas of your code.

How to retrieve AutoInc Values with BDP in Delphi 2005

Sun, 14 Aug 2005 14:42:00 -0500

In this article I’ll use the term “Identity” interchangeably to note Auto generated (from RDMS) values usually for a column representing the primary key of a table. These are called “sequences” in Oracle and “generators” in Interbase.
Actually, there are 3 options to get the identity value back using ADO .NET in general:

Use a batch query (the database obviously has to support this)
Use a stored procedure (as the Insert command) having as an output parameter the “Identity” value (this is the fastest and thus recommended method)
Handle Adapter's RowUpdated /RowUpdating event and issue a "SELECT @@IDENTITY " (in case of SQL Server) query in code in this event handler (slowest)

Parameter exists

Wed, 10 Aug 2005 00:55:00 -0500

You will need the function in this article (http://www.howtodothings.com/ViewArticle.aspx?Article=760) to get this working properly

function ParamExists(const ParamName: string): Boolean;
var
S: string;
begin
Result := GetParameterValue(ParamName, ['/', '-'], ':', S);
end;

Get command line parameters

Wed, 10 Aug 2005 00:53:00 -0500

(* GetParameterValue

GetParameterValue will return the value associated with a parameter name in the form of

/paramname:paramvalue
-paramname:paramvalue

and

/paramname
-paramname

ParamName - Name of the parameter (paramname)
SwitchChars - Parameter switch identifiers (/ or -)
Seperator - The char that sits between paramname and paramvalue (:)
Value - The value of the parameter (paramvalue) if it exists

Returns - Boolean, true if the parameter was found, false if parameter does not exist

typical usage

Parameter
-P=c:\temp\
-S

GetParameterValue('p', ['/', '-'], '=', sValue);

sValue will contain c:\temp\

*)
function GetParameterValue(const ParamName: string; SwitchChars: TSysCharSet;
Seperator: Char; var Value: string): Boolean;
var
I, Sep: Longint;

Get the size of a file

Wed, 10 Aug 2005 00:52:00 -0500

function GetFileSize(const FileName: string): Integer;
var
sr: TSearchRec;
begin
Result := 0;

if FindFirst(FileName, faAnyFile, sr) = 0 then
begin
Result := sr.Size;
FindClose(sr);
end;
end;

BaseForm class

Wed, 10 Aug 2005 00:51:00 -0500

Have you ever found yourself adding the same code to different forms? Well now you can use the following as a base class for all forms.

=============== BEGIN CODE ======================
unit BaseForm;

interface

uses SysUtils, Classes, Forms, Windows;

type
TBaseForm = class(TForm)
protected
    function IsModal(): Boolean;
    procedure KeyDown(var Key: Word; Shift: TShiftState); override;
    procedure ShowError(E: Exception);
    function MsgBox(Msg: string;
      uType: Integer = MB_OK or MB_ICONSTOP): Integer; overload;
    function MsgBox(Msg, MsgCaption: string;
      uType: Integer = MB_OK or MB_ICONSTOP): Integer; overload;
end;

implementation

uses Controls;

MsgBox function

Wed, 10 Aug 2005 00:46:00 -0500

Personally I find both the WinAPI MessageBox and Application.MessageBox and MessageDlg functions cludgy and always add the following function to every app.

function MsgBox(const Msg: string;
MsgType: Integer = MB_OK or MB_ICONSTOP): Integer;
begin
Result := MessageBox(Application.Handle, PChar(Msg),
PChar(Application.Title), MsgType);
end;

requires that Forms.pas is in the uses clause.

Remove ReadOnly flag from file

Wed, 10 Aug 2005 00:43:00 -0500

The following function will attempt to remove the read only flag on a file, you will need the function in this article (http://www.howtodothings.com/ViewArticle.aspx?Article=755).

function RemoveReadOnly(const FileName: string): Boolean;
begin
(* Assume Success *)
Result := True;

(* Make sure the file is read only before
we try and change the attributes *)
if (IsReadOnly(FileName)) then
begin
SetFileAttributes(PChar(FileName), FILE_ATTRIBUTE_NORMAL);

Result := not IsReadOnly(FileName);
end;
end;

Detect if file is ReadOnly

Wed, 10 Aug 2005 00:41:00 -0500

The following function will return True if a file is read only.

function IsReadOnly(const FileName: string): Boolean;
var
sr: TSearchRec;
begin
(* Assume not read only *)
Result := False;

if FindFirst(FileName, faAnyFile, sr) = 0 then
begin
Result := (sr.Attr and faReadOnly) <> 0;
FindClose(sr);
end;
end;