HowToDoThings.com Recent Programming Articles

How To Become a Hacker

omotoed — Mon, 18 Aug 2008 13:54:42 -0500

Hacking is the art of breaking into or penetrating though a secured virtual barrier or firewall normally without the consent of the owner of the virtual environment. Being an act that has always been viewed negatively, hackers always want to keep their identity anonymous to avoid arrest by the authority. Although hacking always poses a serious threat to our systems, to me it is in one way very helpful and that is why I insist on employing computer professionals who poses the skills of hacking.

They help my company by keeping all posible penetration points closed to the public. Furthermore, they help me gather information that keeps my company at a competitive advantage in relation to my competititors.

How To Use a Java Applet

kakulz — Tue, 29 Jul 2008 13:26:02 -0500

How To Use an XML Parser Module

kakulz — Wed, 25 Jun 2008 13:06:22 -0500

eXtensible Markup Language (XML) is the industry standard for exchanging information. XML allows users to define their own tags. These tags are then used to define the data. For example, <author>Syed Feroz Zainvi</author>.

An XML document has hierarchical structure. At the top, there is a document root followed by other nodes, which may in turn have further nodes. There may be attributes and data associated with these nodes.

XML parsers are tools used to read or write to an XML document. These parsers are based on either DOM (Document Object Model) or SAX (Simple API for XML) standards. A comparison of DOM and SAX approaches is given in many books and on websites as well.

How To Use PHP (Hypertext Preprocessor)

jamsam — Tue, 12 Feb 2008 14:46:33 -0600

PHP (Hypertext Preprocessor) is a web development language, where you can develop and create small and big databases/applications with the help of MySQL, Informix, Oracle, Sybase, Solid, PostgreSQL, Generic ODBC, etc. PHP is a server side-scripting language like ASP. Learning PHP (Hypertext Preprocessor) can be fun and challenging. It is not that complicated but requires close attention. Here we will introduce only PHP and MySQL databases.

How To Make a Login System for Your Website

marcosriso — Fri, 21 Dec 2007 15:11:16 -0600

This is a simple login system that has been very reliable and secure for me. I use it myself on my websites, when a simple login system is needed. If you know a little of MySQL and PHP, it is very easy to use.

First, you will need MySQL instaled in your computer. I have XAMMP instaled and I use PHPmyADMIN for accessing my databases. They are free for download; just search for them online. You also need to create a database in your MySQL. And as you proceed, remember that linux server file names are always case sensitives. LOGIN.PHP is not equal to login.php like on WINDOWS servers.

How To Do a Preloader in Flash

vinimaz — Thu, 06 Dec 2007 13:50:16 -0600

I will tell you how to do a simple preloader. Yes, the famous "LOADING!" First, open the flash; second, follow the steps below:

How To Use SelectionFormula in a Crystal Reports Subreport

vicfalmac — Thu, 06 Dec 2007 13:00:38 -0600

If you want to select some data from a subreport inside a report with a different query provided by a VB6 code, you need to follow the steps below:

Create a report and insert a subreport.
Use a Crystal OCX component in your VB6 form.
Create a CrystalReport object. (i.e: Dim Crystal1 as CrystalReport)
Assign the property SubReportToChange: with this property you can assign values to the subreport you want. (i.e: Crystal1.SubreportToChange = "MySubreport")
Pass the selection formula to the subreport. (i.e: Crystal1.SelectionFormula = "Your query here")
Show your report: use the Action event to show your report and the subreport. (i.e: Crystal1.Action 1)

How To Do Web Design Using Web Page Maker

pmzlabis — Fri, 02 Nov 2007 12:49:24 -0500

There is a lot of web design software out there on the market. But, in this instance, I highly recommend that you use Web Page Maker v 2.5 because it's free and so far it has the most user friendly graphical interface.

How To Convert String to Date Using ASP

christphe6 — Fri, 19 Oct 2007 12:40:57 -0500

ASP makes it very easy to convert a string to a date format using built-in VBScript functionality. We're going to use the CDate function to accomplish this. The CDate function has one argument, which is the text to be converted to date format.

Here's how to do it:

Open up your text editor and type the following piece of code:
<%

Dim MyDate

MyDate = "April 12, 1978"

%>
Now, use the function this way to convert the date, and print the new format to the screen:
<%

Response.Write CDate(MyDate)

%>

The result will be displayed in your browser like this:

04/12/1978

How To Learn Syntax In C Programming

zerofox — Fri, 07 Sep 2007 12:21:26 -0500

Learning syntax in C programming will make you understand how to code C in a better way, making you less prone to syntax errors when coding. Below are some conventions in writing C programming that you need to know:

How To Find HTML Editor Freeware

zerofox — Thu, 06 Sep 2007 14:23:34 -0500

Looking for an HTML Editor that is Free? (Freeware). Your free HTML editor should include a WYSIWYG editor, higlight tags, easy-script-install, CSS edit support and the other features you need. Try searching "HTML Editor Freeware" with the Google Search Engine. All you need is the patience to search through the results and find the HTML editor that you're looking for. Here's the procedure you need to know in order to search for the right HTML editor:

How To Send an Escape Sequence in C Programming

zerofox — Thu, 06 Sep 2007 13:50:37 -0500

The Escape Sequences are special characters for formatting; they can be recognized in the code by their characteristic backslash followed by any character that does a certain purpose. These special printing characters are used to make the output readable when printing characters to the screen, file, or other device (such as printer). Below are examples of implementation using escape sequences in C:

Escape sequences in printing to the screen. This example code will show you a program using escape sequence newline ('\n') to separate between two sentences.

How To Protect Your Web Pages

erekhsha — Thu, 06 Sep 2007 13:25:53 -0500

There might be many reasons you why want to prevent visitors from copying your website content. Server side scripts like asp.net and php are always out of the reach of end users, but what about text and images? Sometimes copyright notices don’t seem to be enough and you need to do something more.

So, is there really a way to protect your html pages? The straight answer to this question is no, at least not against the experienced users. But there are a few things you can do to make it harder for the visitors to copy or print the content of your website. Keep in mind that the techniques mentioned here are just a warning to your website visitors rather than a protection for your content. The instant hack to almost all of these tricks is disabling JavaScript. Besides, some browsers, like Opera, do not allow such scripts.

How To Learn Python

mahesh2k — Tue, 04 Sep 2007 11:56:51 -0500

Learning a new language requires understanding the rules and accent of that language. Even programming languages are no exception for this. In open source world, there are lots of uncluttered languages to get your work done quickly. Python is by far the most widely used language which can be used in scripting as well as stand alone applications. It is used by many open source applications and developers.

Obtaining Python. The first step in learning Python is to download and install it. You can download Python from its official site. You can also install Activepython, if you have a windows machine.
If you are using windows: Download the installer and run the executable. This will install IDLE, Module docs, command-line Python and Python manuals.

read more

How To Program in C

zerofox — Thu, 23 Aug 2007 23:40:59 -0500

So you're interested in how to program in C. C is a programming language well known for its power, accessibility through hardware level (low-level programming), efficiency and speed in execution of programs, and its portability to be processed in different operating systems with little or no alteration. In this article I'll try my best to guide you step-by-step building a simple program, nothing too fancy; in this case, we'll just print characters to the screen, which globally is known as Hello World program.

How To Learn PHP Programming

Daniel452 — Tue, 20 Feb 2007 23:45:00 -0600

PHP is said to be an acronym for "PHP: Hypertext Preprocessor", however it's probably just HPP (hypertext preprocessor) rearranged to sound better. It is an open source scripting language, meaning that it's source code is freely available for anyone to work with it. More importantly it is free for you to download and use.

PHP is server side, meaning that it is processed by the web server at the web host rather than the browser, which gives the web developer more control over the outcome. Although it can be used for console scripting, it is primarily used by web developers to implement dynamic content. Dynamic content is created on the fly using a combination of PHP and HTML. HTML is usually used to create the look and feel of the site (a template) and PHP manipulates data from a database.

How To Use PHP to Interact with MySQL

Zamrony P535 — Sun, 03 Dec 2006 19:16:00 -0600

Introduction. This article will discuss how to connect PHP and MySQL, to create a dynamic database-driven website. I will assume that you already have a PHP and MySQL copy installed on your system and they all work. I will also assume that you have basic knowledge about PHP including PHP syntax and how to run a PHP script.
PHP and MySQL. PHP already includes a MySQL module in its distribution, so you won't need to install an additional software module.
Create MySQL user. To create a username and password for your script execute the MySQL console application. You must login as root, then execute this SQL statement:
CREATE DATABASE db_test;
USE db_test;
CREATE TABLE tbl_phonebook
(

read more

How To Write HTML Forms

Daniel452 — Mon, 02 Oct 2006 19:58:00 -0500

A form is an area that contains various form elements to take user input for processing by a special program. There are various form elements as can be seen in the diagram below. The appearance of these form elements, however, may vary based on the browser you are using. This tutorial assumes you have at least a basic knowledge of HTML.

How To Develop in Visual Basic

Randy436 — Fri, 28 Jul 2006 06:48:00 -0500

Microsoft's Visual Basic is one of the most popular programming languages in the world. With it you can create almost any type of application imaginable! Visual Basic is a RAD (rapid application development) environment. What this means is that Visual Basic has dozens of tools to help you create your application fast.

How To Learn HTML Code Tags

Mariya279 — Mon, 26 Jun 2006 08:16:00 -0500

Learning HTML code begins with learning the basic tags. By studying the examples in this article, you should know all of the basic HTML tags that you will need in creating a simple webpage.

First of all, it is important to know that almost every tag has an opening and a closing. When this occurs, we open with <tag>, and close with </tag>. Some tags do not open and close. These are just simply inserted with <tag> and never closed (though in the XHTML standard, they would be typed <tag/>). In the following examples, tags with no slashes in them denote that they must be opened and closed, while tags with a slash after the content (<tag/>) only need to be inserted and never closed.

Note: "<tag>" is not a real tag.

How To Change Your Font Size Using HTML

Mariya279 — Fri, 16 Jun 2006 18:01:00 -0500

Knowing how to change font size on your webpage is almost necessary when creating an attractive, well-organized and sophisticated webpage. You can use the technique to organize, separate and offset information, and just generally improve the look of your webpage. Here are the steps you can follow to change font size on your webpage:

How To Change Your Font Color Using HTML

Mariya279 — Thu, 15 Jun 2006 16:54:00 -0500

Changing your font color can have practical as well as purely fun purposes. It can make your page look more interesting, and it can help you to organize your page. By following these steps, you can change font color on your webpage.

How To Change Fonts Using HTML

Mariya279 — Wed, 14 Jun 2006 13:48:00 -0500

Changing fonts is one way to spice up a webpage. It can also be useful to create headers, emphasis, or differentiation on a webpage. The following steps will allow you to change your fonts with HTML.

How To Choose an HTML Editor

Mariya279 — Mon, 29 May 2006 20:41:00 -0500

Creating a website can be a long, tedious process. Using an HTML editor can streamline the act of writing code to a pleasant degree. If you find yourself in the market for a good HTML editor, it is important to determine what you want from one. By asking yourself the following questions, you can zero in on the HTML editor that is right for you.

How To Create a Website Using HTML and Web Design

Mariya279 — Mon, 29 May 2006 20:06:00 -0500

Creating a website is a big project, but not by any means unattainable. More and more people are finding that they, too, can design and code a website by just spending a few hours in study and deciding on specific goals. The following will outline the basic steps in creating a website.

How To Change Your Cursor Using HTML Code

Mariya279 — Tue, 23 May 2006 20:21:00 -0500

There are plenty of reasons to add flair to your website: presentation, graphical representation of an idea, or just fun. Changing the cursor (what is traditionally displayed as a white arrow controlled by your mouse) is just one of many changes that can be made, but it is an interesting one. It offers many unique options to the webmaster. Following are the steps involved in changing your website cursor.

How To Add Music to a Website Using HTML Code

Mariya279 — Mon, 15 May 2006 17:37:00 -0500

With the influx of websites that allow an individual user to sign up for his very own chunk of webspace, the demand for information on how to add zest to one's webpage is growing larger. Many webspace providers (such as Livejournal and Myspace) allow the everyday user to make minor (or more drastic) adjustments to her personal webpage, and embedding music in the background is one of them. This tutorial will explain the steps that must be taken to add background music to your website.

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;

How BoldTreeView works

Peter5 — Wed, 03 Aug 2005 04:22:00 -0500

This is just a quick set of instructions rather than a comprehensive article. It is a copy of a posting I made in a Borland newsgroup...

I'll give you an example of one I did recently....

01) Set the BoldHandle property to your BoldSystemHandle
02) Double-click the treeview to bring up the editor
03) Click the "Root" element
04) If it hasn't already got a child, click "Add List Fragment"
05) In ElementExpression enter the main OCL, for example
"Customer.allInstances"
06) Set InterpretAsList to True
07) Set ControllerExpression to 'Customer' (including quotes)

What you have now is a root that grabs a list of Customers. The BTV knows that it needs a "node controller" called "Customer" to represent each item in the list (which is why InterpretAsList = True).

Store and Retrieve a Bitmap in ECO

Sun, 17 Jul 2005 17:15:00 -0500

This article demonstrates the basics of how to store and retrieve a Bitmap in an ECO variable.

First create an ECO variable in the class you wish to hold the bitmap, for example:

FCanvas: Byte

Note that we really want a byte array, so right click on FCanvas and select "Go to Definition".
You can now change the definition to byte[] as follows:

private byte[] FCanvas

To write the Bitmap to FCanvas use the following:

ImageConverter ic = new ImageConverter();

System.Byte[] ba = (System.Byte[])ic.ConvertTo(bmp, typeof(System.Byte[]));

FCanvas = ba;

To retrieve the bitmap from FCanvas use the following:

System.IO.Stream str = new System.IO.MemoryStream(FCanvas);

read more

Two functions to evaluate OCL

Mon, 27 Jun 2005 16:47:00 -0500

With the help of Jonas Hogstrom and Jan Nordén I have written 2 functions to evaluate OCL.
First is to evaluate OCL in EcoSpace:
public object EvaluateOclInEcoSpace(IElement rootValue, string ocl)
{
object result = null;
IElement e = ((IOclService)
this.GetEcoService(typeof(IOclService))).EvaluateAndSubscribe(rootValue, ocl,
null, null);
if (e != null)
result = e.AsObject;
return result;
} Second is to evaluate OCL in PS:

public object EvaluateOclInDB(IElement rootValue , string ocl)
{
object result = null;
IElement InternalElement = null;
IOclService oclService = (IOclService)
this.GetEcoService(typeof(IOclService));

read more

Dynamic TableStyles Based on Object Type

Thu, 21 Apr 2005 08:15:00 -0500

Here is an example of using different TableStyles depending on the type of the currently selected object in a DataGrid. I have 2 grids, each hooked to ExpressionHandles. I want to display a different set of columns, depending on the type of object in the top grid.
Firstly the application need to know when a new object has been selected. Here a CurrencyManager is being hooked up. dgStock is a DataGrid, ehRoot is an ExpressionHandle containing the Stock objects.

private cmStock: CurrencyManager;
....
procedure TfrmStock.TfrmStock_Load(sender: System.Object; e: System.EventArgs);
begin
cmStock := CurrencyManager(dgStock.BindingContext[Self.ehRoot]);
Include(cmStock.PositionChanged, Self.StockGridRowChanged);
end;

read more

Reading a tagged value

Peter5 — Wed, 20 Apr 2005 23:42:00 -0500

ECO allows you to add TaggedValues (name/value pair) to your model at design time. Here is how to retrieve the value of a TaggedValue at runtime.

obj.AsIObject() gives IObject
IObject.UmlType gives an IClassifier
IClassifier is an IModelElement, therefore....
IClassifier.TaggedValues['hello'] gives ITaggedValue
ITaggedValue.Value gives the string

ClassDisplayName :=
obj.AsIObject().UmlType.TaggedValues['EcoExtensions.DisplayName'];

IProperty is also an IElement, so you can get tagged values for properties in exactly the same way.

obj.AsIObject().Properties['Name'].UmlType.......

ReEvaluate or ReSubscribe?

Peter5 — Sat, 09 Apr 2005 10:01:00 -0500

This article will explain derived members in ECO. It's primary purpose is to describe the difference between the ReEvaluateSubscriber and ReSubscribeSubscriber parameters when you derive members in code.

One of the excellent features of Bold which have made the transition over into ECO is derived members. A derived member is a bit like a calculated field on a dataset, except it is only calculated the first time you request its value and then that value is cached to processing time.

Take person's FullName as an example. Full name would be calculated as

Result := Title + ' ' + FirstName + ' ' + LastName;

The first important step to creating such an attribute in ECO is to mark the attribute Derived. It is actually possible to specify some "Derivation OCL" and have the ECO system derive everything for you

title + ' ' + firstName + ' ' + lastName

read more

A Multi-Client-ECO application example.

Sat, 09 Apr 2005 05:00:00 -0500

The application we are going to build can be used for capturing worktime and breaks during the worktime. The worktime can be captured with multiple clients and the server application provides a view of all the data captured.
[The client part]

You start with setting up a winform eco application. This application shall be the client. I named it WorkTimeClient.
You need to have the UML Classes in a package so that you can add them later on to the server application.

Create the following model:

read more

Turning on/off ECO logging

Peter5 — Thu, 07 Apr 2005 03:23:00 -0500

ECO II has a new feature in Update 2 which makes it easier to see what it is doing behind the scenes.

When you run your app you can look in the messages window of the Delphi IDE and see what is happening. You can turn on/off switches for different areas of ECO including OCL, PMapper, etc by setting the following options.

Borland.Eco.Logging.EcoLogSwitches.LogOcl := false/true;
Borland.Eco.Logging.EcoLogSwitches.LogPMapper := false/true;
Borland.Eco.Logging.EcoLogSwitches.LogRegions := false/true;
Borland.Eco.Logging.EcoLogSwitches.LogSql := false/true;
Borland.Eco.Logging.EcoLogSwitches.LogSqlMeta := false/true;
Borland.Eco.Logging.EcoLogSwitches.LogValidation := false/true;

Automatically setting the MaxLength in your GUI

Peter5 — Tue, 15 Mar 2005 08:14:00 -0600

As of D2005 udpate #2 there is a new helper class in the ECO framework named MaxLengthSupportFunctions.

Normally when you databind an EditBox for example to an ECO object you are able to type endlessly despite the fact that you may have set the Eco.Length of the attribute to something small like 32.

This new helper class will identify such situations and automatically set the MaxLength property. All you have to do is to execute the following line of code after your rhRoot has been set.

Borland.Eco.WinForm.MaxLengthSupportFunctions.UpdateMaxLengths(Controls);

Disabling multiplicity constraints

Peter5 — Tue, 15 Mar 2005 05:37:00 -0600

If you have ever tried reading constraints from an ECO model you have probably noticed by now that there are lots of auto-generated multiplicity constraints.

I personally like to add my own constraints for multiplicity so that I can specify a more concise error message

Customer required:customer <> nil

To disable multiplicity constraints you need to attach a .net attribute to your EcoSpace like so

[UmlTaggedValue("Eco.GenerateMultiplicityConstraints", "False")]
public class ProjectManagerEcoSpace: Borland.Eco.Handles.DefaultEcoSpace

Evaluating constraints

Peter5 — Sat, 26 Feb 2005 04:21:00 -0600

Before updating the database with changes to your objects it is wise to check that the object is in a valid state first. ECO allows you to model constraints against your classes by adding a list of OCL expressions, but does not evaluate the expressions at any point.

It is in fact the responsibility of the application to check whether or not an object is valid or invalid, and to then decide what to do about it. One approach is to check the validity of each object before it is saved, this can be achieved in the UpdateDatabase() method of your EcoSpace.

read more

Sending HTML emails with ICS

Thu, 10 Feb 2005 10:09:00 -0600

procedure THtmlMailForm.SendButtonClick(Sender: TObject);
begin
if FRunning then begin
MessageBeep(MB_OK);
Display('**** ALREADY RUNNING ****');
Exit;
end;

FRunning := TRUE;
try
{ Give the component the various data he need }
HtmlSmtpClient.PlainText := PlainTextMemo.Lines;
HtmlSmtpClient.HtmlText := HtmlTextMemo.Lines;
HtmlSmtpClient.EmailImages := ImageFilesMemo.Lines;
HtmlSmtpClient.EmailFiles := AttachedFilesMemo.Lines;

{ Initialize all SMTP component properties from our GUI }
HtmlSmtpClient.Host := HostEdit.Text;
HtmlSmtpClient.Port := PortEdit.Text;
HtmlSmtpClient.SignOn := SignOnEdit.Text;
HtmlSmtpClient.FromName := FromEdit.Text;
HtmlSmtpClient.HdrFrom := FromEdit.Text;
HtmlSmtpClient.HdrTo := ToEdit.Text;
HtmlSmtpClient.HdrCc := CcEdit.Text;
HtmlSmtpClient.HdrSubject := SubjectEdit.Text;

read more

Evaluating in-database OCL in code

Peter5 — Thu, 10 Feb 2005 04:42:00 -0600

In a form etc we can evaluate OCL in the DB by using an OclPSHandle, but how do you evaluate OCL in the DB in code?

This tip thanks to Jan Norden from Borland.
IOclService oclService =
(IOclService) GetEcoService(typeof(IOclService));
IPersistenceService persistenceService =
(IPersistence) GetEcoService(typeof(IPersistenceService));

AbstractCondition cond =
OclService.CreateRetrieveCondition(RootValue, EffectiveVariables(), Expression);

InternalElement = persistenceService.GetAllWithCondition(cond, MaxAnswers, Offset);