Delphi KB: Delphi for Win32 Topic

This primer is intended for those just getting started in Delphi and focuses on displaying things.

Create a classic "Hello, World" Windows native code Console App using Delphi. This tutorial is based on Borland Developer Suite 2006 but you can use any version of Delphi you wish. In this tutorial, you will create a classic "Hello, World!" windows console application. A console application is a type of Windows application that has FULL access to the Win32 API, but it's GUI is limited to a DOS-like text window. When Windows starts a console application, it creates a text-mode console window where the program can display text and the user can interact with the program via the keyboard.

Beginners example of creating and using a class. Early versions of Delphi use the standard OO private, protected, and public visibility specifiers plus add published for RTTI info. Later versions of Delphi add strict private and strict protected for a true OO implementation.

When you want the exception to be the rule. A technique for handling exceptions in Borland Delphi's Object Pascal.

To resize the list box of a combobox, you merely need to send the Windows API message: CB_SETDROPPEDWIDTH to the combo box.

I always found the sleep command in ObjectPAL very useful. The following code does about the same thing in Delphi. It makes use of GetTickCount which is a Win32 API call that retrieves the number of milliseconds that have elapsed since the system was started, up to 49.7 days.

Although Object Pascal doesn't have a native associative array, many developers just use a TStringList. Others have implemented a true associative array in Object Pascal. Search the Internet for TStringHash and THashedStringList classes for examples.

TStringList Example
Object Pascal doesn't have a native associative array, but you can use a TStringList the same way. (Alternatively, search the Internet for TStringHash and THashedStringList classes for implementations of a true associative array).

David Intersimone ("David I") of Borland demonstrates the latest versions of the Borland Developer Studio 2006 Product

Can I call a DotNet DLL from my Delphi Win32 application? For example, with Delphi 7 or Delphi 2010?

Correctly implementing COM collections.

Windows sends the WM_GETMINMAXINFO message when the user tries to resize a window either by clicking the maximize button or dragging the borders of the window. By creating a suitable message-response method, you can specify the minimum and maximum window sizes for that form.

Use SetWindowRgn API call to make a round form. The SetWindowRgn function sets the window region of a window. The window region determines the area within the window where the operating system permits drawing. The operating system does not display any portion of a window that lies outside of the window region.

Simply use this function in the FormCreate event:

The steps for creating an application server with Delphi 2005, steps that were first introduced with Delphi 3.

If you've written any ISAPI DLLs, and tried to debug them, you've learned that it isn't exactly a trivial task. This little code snippet can often eliminate much of the pain.

Delphi for Win32 supports abstract class members using the abstract keyword. You can even instantiate instances of a class that contains abstract members. Then you override each abstract member in a descendant class with Override. Delphi does not support setting an entire class as abstract. You can create an abstract class (a class with one or more abstract methods), but there is no way to tell the compiler to not allow the instantiation of the abstract class. Delphi does not support abstract member properties directly. To implement an abstract properity, make use of abstract methods. That is, you can read a GetPropertyX abstract function and write to a SetPropertyX abstract procedure. In effect, creating  an abstract property.

Delphi supports both static and dynamic arrays.

Delphi uses := for it's assignment operator.

Object Pascal doesn't have a native associative array, but you can use a TStringList the same way. (Alternatively, search the Internet for TStringHash and THashedStringList classes for implementations of a true associative array).

In Delphi programming language (Object Pascal), all classes ultimately inherit from the base class TObject.

How often have you started a new Delphi project, then spent some time fleshing out the default main form provided by Delphi?

This task only needs to be done once or twice. Delphi then allows us to re-use this work at the start of each new project.

Source code is included.

In this first installment of a New Knowledge Base Series I'll discuss The TForm.OnCloseQuery Event which too frequently goes unhandled.

Object Pascal is generally not case sensitive.

Delphi allows you to extend an existing class without using inheritance. Buggy in 2005 and not officially supported but stable and usable in 2006 and above. You declare a class helper similiar to how you declare a class but use the keywords class helper for.

• You can name a helper anything.
• Helpers have access only to public members of the class.
• You cannot create an object instance directly from a class helper.
• self refers to the class being helped.

Object Pascal supports static methods, but not static member fields. For static member fields, use traditional Pascal-like global variables. Since Object Pascal is a hybrid language, you can use global functions and data so the need for class methods is diminished but still useful. Delphi 1-7: All classes in a unit are friendly (see eachother's private members), some developers like to put each class in it's own unit and reserve putting multiple classes in the same unit until they wish to implement friendly classes. Delphi 2005+: New strict keyword allows you to indicate friendly.

Declare your class in the Interface section. Then implement the class in the Implementation section.

Object Pascal requires the semi-colon after the "declaration" part.

Delphi uses // for a single line comment and both {} and (**) for multiple line comments. Although you can nest different types of multiple line comments, it is recommended that you don't. A special comment. Delphi compiler directives are in the form of {$DIRECTIVE}. Of interest for comments is using the $IFDEF compiler directive to remark out code.

Common comparison operators:

In Delphi, you define constants similar to how you define variables but use the Const keyword instead of the Var keyword. Declare global constants in a unit's interface section and unit constants (scope limited to unit) in the implementation section. Declare local constants above the begin..end block.

In Delphi, use the constructor keyword to signify which method or methods are constructors for a class. It is traditional but not required to use a procedure called Create.

In addition to having multiple named constructors, you can overload constructors.

Delphi is a hybrid language so you can create either class methods (functions and procedures) or you can create global functions and procedures. When a function or procedure is part of a class, it is a class method.

As with C++, your custom routine must come before it's first usage or you have to prototype it in the Interface section.

Note: Contrast Delphi with Delphi Prism which is an OOP language (everything is within a class). Both Delphi and Delphi Prism are based on Object Pascal but implement OOP features differently and have some syntax differences too.

Delphi create native code Windows applications so you can create an EXE with no dependencies that will run on any Windows computer. If you add dependencies (reports, database libraries, DLLs, etc.) use a Windows installer to build an installation program.

D2007 and D2009 are bundled with InstallAware Express CodeGear Edition installer.

Object Pascal uses a standard virtual destructor named Destroy which is called by the standard Free method. All objects are dynamic, so you need to call MyObject.Free method or the FreeAndNil(MyObject) routine for each object you create.

Languages Focus: Development Tools

Primary development tool(s) used to develop and debug code.

Borland Delphi editor tips and tricks.

Length() or SizeOf() will correctly identify an unassigned string variable or an empty string.

Languages Focus: End of Statement

In coding languages, common End of statement specifiers include a semicolon and return (others exist too). Also of concern when studying a language is can you put two statements on a single code line and can you break a single statement into two or more code lines.

Many objects in Delphi have events you can use to trigger code. For example, when you add a form to your project you have access to the form events such as onCreate, onShow, onHide, onDockDrop, etc. In addition, Delphi offers module level events initialization and finalization sections.

Delphi also offers a try...finally where code will execute in the finally section no matter what. It's common to put a try...except inside a try...finally:

Common source code file extensions include:

• .BDSPROJ - Project, Borland Developer Studio project file holds compiler options, etc. This is the file you open.
• .DCU - Delphi Compiled Unit file.
• .DFM - Delphi Win32 form file (a text resource file).
• .DPR - Delphi project file. Primary project "source" file.
• .PAS - Delphi unit source file.

Our Delphi Gazette ran for a vew years in the late 90s. This page archives 1998.

Notice in the more complete example that the semicolon for the begin..end block after end is not included. That tells the compiler something else is coming (the statement is not finished). Also note the semicolon is missing right before the final "else" statement.

Note: The following example uses floating point literals. In Delphi, to specify a fractional floating point literal between 1 and -1, you preceed the decimal with a 0; otherwise, you will get a compiler error (i.e. .1 + .1 does not work).

In Delphi, you use the class keyword followed by the parent class in parens. If you leave out the parent class, your class inherits from TObject.

Delphi does not support multiple implementation inheritance. Each class can have only one parent class (a single inheritance path). In Delphi, you can use multiple interface usage to design in a multiple class way horizontally in a class hierarchy.

In Delphi, you can inline assembler code using the asm keyword.

Delphi introduced developer defined function and procedure inlining with Delphi 2005. Use the inline keyword to tell the compiler to inline a routine. Since Delphi will always inline the routine, make sure you test for speed because inlining a routine can lead to slower code under some circumstances.

You specify an interface in the type block just like you do for a class but you use the interface keywoard instead of the class keyword and in the interfaces section only. Since interfaces, by definition, do not have any implementation details, all you do is specifiy it in the type block.

Delphi LeftStr

Literals are single quoted (the apostrophe) as in 'Prestwood'. If you need to embed an apostrophe use two apostrophies in a row.

Delphi logical operators:

In Delphi, member events are essentially properties of the type method pointer.

In Delphi, it is common to start all member fields with "F" as in FName and FAge. You can initialize the value of member fields. Delphi member fields do not support static data. The workaround is to use the hybrid nature of Delphi and use a unit variable (a variable declared in the implementation section of a unit).

Delphi uses the keywords procedure and function. A procedure does not return a value and a function does.

Specify Delphi member modifiers as follows:

reintroduce; overload; [binding modifier]; [calling convention]; abstract; [warning]

The binding modifiers are virtual, dynamic, or override. The calling conventions are register, pascal, cdecl, stdcall, or safecall. The warnings are platform, deprecated, or library. Additional directives include reintroduce, abstract, class, static, overload, and message.

Delphi uses a special property keyword to both get and set the values of properties. The read and write keywords are used to get and set the value of the property directly or through an accessor method. For a read-only property, leave out the write portion of the declaration.

You can give properties any visibility you wish (private, protected, etc). It is common in Delphi to start member fields with "F" ("FName" in our example) and drop the "F" with properties that manage member fields ("Name" in our example).

Up until D2005, private and protected were not implemented strictly. Starting with D2005, a traditional strict versions of OOP are supported using the strict keyword. OO purist will want you to use strict private over private and strict protected over protected. I suggest you follow that advice until you both fully understand the differences and have a specific need. Delphi offers a special published specifier which is the same as public members but runtime type information (RTTI) is generated.

Object Pascal

• Operator - Yes. But not Pascal.
• Method - Yes.  

In Delphi, you specify a virtual method with the virtual keyword in a parent class and replace it in a descendant class using the override keyword. Call Inherited in the descendant method to execute the code in the parent method.

Language Overview: Delphi programming language is a type-safe language consisting of hybrid traditional Pascal and OOP features. You code either in a traditional approach using functions, procedures, and global data, or you code using an OOP approach, or a mixture of both.

Target Platforms: Delphi for Win32 is most suitable for creating native code Win32 applications that run on Microsoft Windows.

Object Pascal allows parameters of the same type to be listed together, separated by commas, and followed with a single data type (more params of different data types can follow, after a semi-colon). The default for parameters is by value. For by reference, add var in front of the parameter. Object Pascal also offers constant parameters where you add const in front of the parameter. A constant parameter is like a local constant or read-only parameter the compiler can optimize. You cannot assign a value to a constant parameter, nor can you pass one as a var parameter to another routine.

Although pointer data types in Delphi coding are less important and not required for most general coding, Delphi fully supports developer defined pointers. Use a carrot (^) to declare a pointer data type. Use the @ operator or Addr function to return the current address of a variable.

Delphi supports the following types of polymorphism:

• Parametric Polymorphism (Method Overloading)
• Inheritance-Based Polymorphism
• Interface-Based Polymorphism (Interfaces)
• Ad-Hoc Polymorphism (Operator Overloading)

With Delphi, use the sealed keyword to prevent a class from being inherited from and use the final keyword to prevent a method from being overridden.

Within the implementation of a method, the identifier Self references the object in which the method is called. The Self variable is an implicit parameter for each object method.
A method can use this variable to refer to its owning class.

Use the + operator to concatenate two strings. Use IntToStr to convert an integer to a string and FloatToStr to convert a floating point number to a string.

An operation with only one operand (a single input). In Object Pascal, a unary operator always precedes its operand (for example, -B), except for ^, which follows its operand (for example, P^). The Delphi unary operators are +, -, and ^ (pointer).

The TYPE operator is also a unary operator and is�evaluated at compile time. The TYPE operator returns the size in bytes of the operand,

Declare global variables in the interface section of a unit, variables declared within the implementation section (but not within a method) have a scope limited to the unit. You declare local variables in a var block outside (above) your begin..end code block. You cannot declare variables in-line (inside begin..end). You can initialize global and unit variables but you cannot initialize local variables. Delphi offers many variable types. Some common variable types include String, WideString, PChar, Integer, Boolean, Single, Double, Pointer, and Variant.

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Use Windows API GetSystemMetrics with SM_CLEANBOOT parameter to determine how Windows was started.

This code snippet shows you how to get your NIC MAC address using Borland Delphi.

Windows XP incorporates a "theme manager," and includes a newer version of comctl32.dll. Together, they help produce the unique XP Look. Later versions of Delphi are equipped to take advangage of this. But what if you have to maintain a Delph 5 application, and would like to spruce it up to look like a real XP program?

To insert a GUID into code using the Delphi Editor, use Control + Shift + G.

However, if you are using either the Visual Studio or Visual Basic key mapping emulation, use Control + Alt + G.

What are the benefits of Win32/64 native code such as in Delphi over .Net?

Format the IF/Endif for easy reading. I have found this to be easy to read and follow:

To indent the structure and line up the parenthesis makes it, I feel, much easier to read.

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You cannot create a Delphi unit with the same name as is already in use. For example, do not create a buttons.pas unit for your application because the VCL already has a Buttons.pas unit. The solution is to rename your unit.

You can record a series of keystrokes to be played back for quick changes in code. Use Ctrl+Shift + R to begin recording, Ctrl+Shift+R again to stop the recording, then Ctrl+Shift+P to play recording.

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What is a sealed class?

How to enable SSL transactions with the Indy HTTP v9 component.

Delphi's TDBGrid is an incredibly useful component; one you'd expect to find in any professional development tool.

One of it's handy behaviors is that users can click in column headers and drag to rearrange column ordering to their liking.

Unfortunately, TDBGrid doesn't offer the developer any really easy way to rearrange grid columns from code. This is inconvenient because you might offer the user a choice of various columns upon which they can search, and it would be nice to make their chosen column the leftmost - at least. Often it makes sense to rearrange other columns as well.

This little class allows you to do that.

It has no exposed methods, and only two properties, so it's incredibly easy to use.

Read on to learn how it works and to get the code.

In 1995 Borland revolutionized the world of software development when they introduced Delphi.

It had the distinction of being the first integrated development environment (IDE) featuring a fully object-oriented language and a blazing-fast compiler that produced highly optimized, native Intel machine code. Programs written in Delphi were among the fastest in existence – and still are.

After all these years, is Delphi still relevant?

You bet it is! (And, in many cases, it is still your best bet.)

Here's why...

The online tutorials for these controls use IIS, this post describes the same use with the Cassini web server

New virus targets old versions of Delphi but not the applications developed with Delphi and not the current Delphi versions, just Delphi itself. I detest the jerks that write viruses and other forms of malware.  But this one really gets my goat generally because it was a virus that targeted my favorite best-of-breed development tool and specifically because ZDNet reported the problem in a way that implies it targets applications developed by Delphi. Despite ZDNet's tag line, the virus targets old versions of Delphi (4, 5, 6, and 7) but not the applications developed with Delphi and not the current Delphi versions. I sure hope the way ZDNet chose to report this issue doesn't hurt Embarcadero, the owner of Delphi, because of a virus that attacks pre-Embarcadero versions of Delphi.

Back in the wild and wooly days of C/PM, DOS, and early versions of Windows, we programmers could store our data pretty much anywhere. It might not have been a good idea, but we could get away with it.

Things have changed drastically!!

If your program stores data, you need to know where it belongs, and that varies quite a bit from one version of Windows to others.

Read on to find out where your data belongs.

Microsoft's various COM technologies allow developers to write programs that can interoperate with other programs.  This is great stuff!

Not surprisingly, Delphi makes it pretty easy to work with OLE, Active-X, OCX, etc.

But there's a nasty surprise awaiting you when you try to do this in a DLL you're creating, possibly even in a different thread of an executable, too.

Here we expose the problem - and the solution.