Delphi – for … in on enumerated data types

I like enumerated type a lot.
The allow you to perfectly describe what the members of such a type actually mean, much more readable than a bunch of integer constants!

Given an enumerated type like TTraphicLightColors

type
  TTraphicLightColors = (Red, Orange, Green);

I always wondered why  - since the for ... in statement was added to the structured statements part of the Delphi language – it is not possible to use a for … in statement like the this:

</span>
<pre>var
  TraphicLightColor: TTraphicLightColors;
begin
  try
    for TraphicLightColor in TraphicLightColor do
      ShowValueAsTraphicLightColor(Ord(Value));
    // [DCC Error] EnumerationEnumeratorDemoProcedures.dpr(63): E2430 for-in statement cannot operate on collection type 'TTraphicLightColors'
end;

Somehow, for … in expects a collection type.
A request for the for … in do on enumerated types compiler feature is in QC, but it is closed with reason “Won’t do”.

Back in Delphi 2007, I tried working around this by writing a type implementing the GetEnumerator pattern myself, but got Internal Errors when compiling anything but the most basic sample.

Until today, where I found how I could get that most basic sample to work!
It is an example on how you could implement this: it is research, so you decide if you find the result practical enough to use yourself.

Delphi operator overloading: table of operators, names, and some notes on usage and ‘glitches’

Operator overloading is a very nice feature of the Delphi language.
However. the Delphi documentation on Operator overloading is not completely right.

Below is my table of what I found out so far, and some notes.

It is part of my “Nullable types in Delphi” session that I gave on some conferences.
The downloads for that session contain more detailed information.

This is just an abstract to get you going and a try to answer this operator overloading question on Stackoverflow.
Download the full presentation to get more in depth information.

Let me know if you need more information.

Notes

Operator overloading

Add your own “behaviour” to operators

• Win32: Works only for records, not classes!
• An operator and the operand(s)
  are being implemented worden by a “class operator”;
  this is a kind of class method with name and argumen(s)

Example:

• Multiplication X : = A * B;
• Operator: *
• Name: Multiply
• Operands: 2 -> two parameters

type
  TMyRecord = record
    class operator Multiply(A, B: TMyRecord): TMyRecord;
  end;

Documentation is not correct!

• http://docs.embarcadero.com/products/rad_studio/delphiAndcpp2009/HelpUpdate2/EN/html/devcommon/operatoroverloads_xml.html
• http://docwiki.embarcadero.com/RADStudio/en/Operator_Overloading
• Win32 only records; .NET classes and records
• BitwiseNot does not exist (use LogicalNot)
• At least 1 operand must be of the same type as your record data type
• Result type may be anything

Watch the result type of comparison operators!

Tips:

• Some operators should be overloaded pair-wise
  = and <>
  shl and shr
  < and >=
  > and <=
  dec and inc
  + and -
  / and *
  div and mod
• Prefer Explicit over Implicit operators
  • Beware of the built-in type coercion (implicit operators)
  • e.g
    • Byte to Integer;
    • Integer to Double;
    • Variants from/to anything!

Table of operators

operator	#	usage	name	cagetory	*
and	2	R := A and B;	BitwiseAnd	bit
not	1	R := not A;	//BitwiseNot	bit	glitch: does not exist!
or	2	R := A or B;	BitwiseOr	bit
xor	2	R := A xor B;	BitwiseXor	bit
() cast	1	R := TValue(A);	Explicit	conversion
:=	1	R := A;	Implicit	conversion
operator	#	usage	name	category	*
round	1	R := Round(A);	Round	function
trunc	1	R := Trunc(A);	Trunc	function
and	2	R := A and B;	LogicalAnd	logical
not	1	R := not A;	LogicalNot	logical
or	2	R := A or B;	LogicalOr	logical
xor	2	R := A xor B;	LogicalXor	logical
operator	#	usage	name	category	*
+	2	R := A + B;	Add	binary
/	2	R := A / B;	Divide	binary
div	2	R := A div B;	IntDivide	binary
mod	2	R := A mod B;	Modulus	binary
*	2	R := A * B;	Multiply	binary
-	2	R := A – B;	Subtract	binary
operator	#	usage	name	category	*
shl	2	R := A shl B;	LeftShift	binary	name is confusing
shr	2	R := A shr B;	RightShift	binary	name is confusing
-	1	R := -A;	Negative	binary
+	1	R := +A;	Positive	binary
dec	1	Dec(A);	Dec	self
inc	1	Inc(A);	Inc	self
operator	#	usage	name	category	*
=	2	R := A = B;	Equal	comparison
>	2	R := A > B;	GreaterThan	comparison
>=	2	R := A >= B;	GreaterThanOrEqual	comparison
<	2	R := A < B;	LessThan	comparison
<=	2	R := A <= B;	LessThanOrEqual	comparison
<>	2	R := A <> B;	NotEqual	comparison

–jeroen

Delphi – list of posts about hidden registry entries

There are quite a few registry tricks that you can perform to influence the Delphi IDE.

If you have any registry settings to share, please let me know by posting a comment below, or filling out the contact form.

This summary will be enhanced over time:

• 20091015 – Chris Bensen – Delphi Tips and Tricks – Additional Files
• 20090509 – René Rikkers - Delphi 2009 broken after installing Update 2
• 20080912 - Matthias Eissing - C++ Builder 2007 und der Remote Debugger
• 20071017 – Chris Bensen – Delphi and C++ Builder IDE Memory Usage Tip
• 20070928 - Sergio Cardoso - Are you nuts?
• 20070920 - David Clegg - Maximizing your RAD Studio 2007 experience
• 20070509 - Fredrik Haglund - How do I get my application with Paradox tables to work on Windows Vista?
• 20070313 – Chris Hesik – Source has been modified. Rebuild?
• 20061019 - Steve Trefethen - IE7 is now available get your BDS reg file here
• 20060110 – Mark Edington – Delphi Startup Times and the Kitchen Sink
• 20051219 - Adam Markowitz - Displaying macros in Code Completion (C++Builder2006)
• 20051209 – Adam Markowitz – Hidden feature, anyone?! (Delphi2006)
• 20051208 - Chris Hesik - BDS 2006 Debugger and .NET 2.0 compatibility
• 20040929 – Corbin Dunn – Delphi 8 Tips, Tricks and Speed Improvements
• 20040923 - Allen Bauer - Newsgroups leakage…
• 20041228 – Daniel Polistchuck – Delphi 2005 and Janeva 6.5
• 20040313 - Allen Bauer - Revenge of the Automated IDE Incident reporting
• 20040217 – Allen Bauer – Delphi 7 packages for using the Delphi 8 Win32 compiler
• 20031029 – Allen Bauer – Editor pair highlighting

Have fun with them!

–jeroen

Delphi – finding the VERxxx define for a particular Delphi version

Finding the correct VERxxx conditional define for a particular Delphi version is asked by a lot of people.

Even the first link in the above search, does not contain the full list!
But: JCL comes to the rescue

The JCL file JEDI.INC usually (read: like 99.999% of the time) is up to that with that information soon.
Currently, it contains all the defines starting with Delphi 1, up to Delphi 2010.

You can always browse the to JEDI.INC with this link to the sourceforge trunk.

In fact that file contains a lot more useful defines.
Actually, having the JCL and/or JVCL at hand is a very good practice: it is filled with high quality code that solves a lot of everyday problems.

Note:

VER190 (by some people attributed to the wrong Delphi version) is only used by Delphi 2007 for .NET (Delphi 2007 for Win32 used VER185 by itself and shares VER180 with Delphi 2006 for Win32).

The number 13 (in between Delphi 2009 aka Delphi 12, and Delphi 2010 aka Delphi 14) was never used as a Delphi version number
Since Delphi is mainly developed in the USA, and since a lot people there have Triskaidekaphobia, they showed mercy to those and skipped Delphi 13.

–jeroen

Delphi – hardcore debugging the intialization of your app, dlls and packages

Recently we got involved with a client having a large and complex application that (historically) consists of

1. A main .EXE that loads
2. Many DLLs
3. Underlying BPLs

One of the biggest problems is debugging the startup sequence.
Somehow, when the Delphi IDE loads DLLs in the initialization sequences of units, it looses its ability symbol tables.

This article describes a few tips on how to debug those, especially where to put breakpoints.

Te Waka o Delphi · Absolute for Beginners

Jolyon Smith just published a great article about using the absolute keyword in Delphi.

When used with care (just like the with or goto keywords), absolute can make your code much easier to maintain.

Recommended reading!

–jeroen

Turbo Power projects finally coming alive again? Nick Hodges is now tpsfadmin on SourceForge – DelphiFeeds.com

Nick Hodges just posted he has become the tpfsadmin on sourceforge: the administrative account for the Turbo Power tools and libraries.

It is not an officially sponsored Embarcadero thing, but at best semi official.

However, it is an admirable step into getting the Turbo Power tools and libraries updated in one central place again.

Those tools include OnGuard, Orpheus, SysTools, FlashFiler, B-TreeFiler, Async Professional and many others.

So if you have your own fork of any of the Turbo Power code from sourceforge, then please drop Nick a note.

Many thanks to Nick!

–jeroen

Delphi – record and class helpers: an overview of useful links

At the EKON13 conference, I will be presenting a talk about record and class helpers.

This morning, my laptop did “beeeeeeep beep beep” followed by a deadly silence.
It will take a while before my spare laptop arrives at the hotel and my Vista and VM’s are working again.
So I needed to redo some of my preparations to make sure that I can do a ‘plan B’ if restoring on the spare laptop fails.

Hence below a list of useful links, not yet in a particular order, but it saves you browsing through search engine results sifting the good from the not so good info.

• Delphi About: extending TStrings.Add to accept Variant(s)
• The Wiert Corner: adding for … in support for TComponent.Components
• The Wiert Corner: getting SoureFileName from EAssertionFailed
• Mike Prestwood: General description on class helpers
• Delphi Geek: class helper enumerators
• Joe White: unfinished ‘virtual methods on class helpers’ feature of the day
• Anders Melander: TApplicationVersionHelper for TApplication
• David Glassborrow: class helpers, good or bad?
• David Glassborrow: TListHelper, TStringsHelper and TStreamHelper
• Hallvard Vassbotn: how CodeGear did the Delphi 2007 GlassFrame support using class helpers
• Jan Goyvaerts: What are you missing if you are stuck with Delphi 7
• Stackoverflow: class helpers not working in the debugger evaluation
• The Wiert Corner: class helper to circumvent ‘with’
• Stefan Cruysbergs: how I wrote some class helpers to develop .NET Compact Framework applications with Delphi for .NET
• Nick Hodges: new language features since Delphi 7
• Marco Cantú: class helper example for .NET Compact Framework development with Delphi for .NET
• Jon Shemitz: book – .NET 2.0 for Delphi programmers, page 235
• Dr Bob: IsVowel function using class helper for TCharacter
• Alexandru Chiobanu: class helper for TCustomForm showing Windows 7 support
• Jim McKeeth: CodeRage II session and overview of links on class helpers
• Jim McKeeth: replay of CodeRage II session on class helpers

http://www.davinciunltd.com/code/delphi-class-helpers/

CodeRage 4 session material download locations changed – CodeCentral messed up

Somehow, CodeCentral managed to not only delete my uploaded CodeRage 4 session materials (the videos are fine!), but also newer uploads with other submissions.

Since I’m in crush mode to get the BASTA! and DelphiLive 2009 Germany sessions done, and all Embarcadero sites having to do with their membership server perform like a dead horse, I have temporary moved the downloads, and corrected my earlier post on the downloads.

I have notified Embarcadero of the problems, so I’m pretty sure they are being addressed on their side as well.
Edit 20090919: Embarcadero indicated that between 20090913 and 20090914 there has been a database restore on CodeCentral. Some entries therefore have been permanently lost.

When I get back from the conferences, and CodeCentral is more responsive, I’ll retry uploading it there, and correct the posts.
In the mean time, be sure not to save shortcuts to the current locations, as they are bound to change.

The are the new download locations can all be found in my xs4all temporary CodeRage 4 2009 download folder.

This is the full list of my CodeRage 4 sessions and places where you can download everything:

CodeRage 4: session replays are online too!

Embarcadero has made available the replays of the CodeRage 4 sessions.
You can find them in the CodeRage 4 sessions overview.

In order to download them from that overview, NOTE: To access this session replay, you must be logged into EDN. you can login or sign-up (which is free).

To make it easier to find all the relevant downloads, below is an overview of my sessions and their links.

Let me know what you use it for, I’m always interested!

Update 20090918: changed the download locations because CodeCentral messed up.