A bit more than a year ago, I wrote about Delphi: you should avoid the with statement as it makes your code less future proof. That caused some nice comments on the blog, and some more on LinkedIn where Paul Foster mentioned it in a thread ‘Jeroen Pluimers makes a case against “with” statements.‘ Both interesting reads, especially the reasons that people use or avoid with, or keep its use in balance. There is one set of comments I want to emphasize: refactoring multiple with statements into a one function and a call per former with. Read the rest of this entry »
Archive for the ‘Delphi 8’ Category
Delphi `with` post and discussion revisited (via: wiert.me and LinkedIn)
Posted by jpluimers on 2014/06/11
Posted in Borland Pascal, Delphi, Delphi 1, Delphi 2, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Development, Pascal, Software Development, Turbo Pascal, With statement | 19 Comments »
Delphi multithreading and DLL exports: watch your exceptions (via: Stack Overflow)
Posted by jpluimers on 2014/06/03
Talking about Danny Thorpe: he also posted a nice hint on threading methods for ancient Delphi versions that equally applies to DLL exports in any Delphi version, even any programming environment.
Recently, I had to do some surgery in such a Pre-Delphi 6 application, and I was really happy to remember this answer: it instantly solved some process crashes, and the added logging allowed for investigating the actual cause.
Note that this tip isn’t just a good advice for old Delphi versions.
Even in younger Delphi versions, you have to watch methods that can be called from outside a regular Delphi context, for instance exported methods.
Heck, it applies to virtually any development environment: exceptions usually are very specific to that environment and should never cross a process boundary.
Summary
Take the approach below
- for Execute methods in your own thread classes in Delphi 5 or earlier
- for any method that can be called externally (like DLL exports) Read the rest of this entry »
Share this:
Posted in Delphi, Delphi 1, Delphi 2, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi x64, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Development, Software Development | Leave a Comment »
Delphi: Design-Time Component Name Limited to 63 characters (via: Vin Colgin – Google+)
Posted by jpluimers on 2014/05/05
I learned something new today (thanks Vin Colgin) the Delphi Design-Time Component Name is Limited to 63 characters.
Uwe Raabe found out that this an Object Inspector thing due to this constant in DesignIntf.pas:
const MaxIdentLength = 63;
It has been probably there since Delphi 1 and has been documented on-line since at least Delphi 2007.
I remember having had long (like 100+ character) identifiers in source code, but not in the Object Inspector.
Now I know you can’t (:
–jeroen
via: Vin Colgin – Google+ – Delphi: Design-Time Component Name Limited to 63 characters….
Share this:
Posted in Delphi, Delphi 1, Delphi 2, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi x64, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Delphi XE5, Delphi XE6, Development, Software Development | 4 Comments »
GExperts 1.37 available for Delphi XE6..6.02, but not for Appmethod (via: Download | GExperts)
Posted by jpluimers on 2014/04/19
GExperts 1.37 (commit 875, but no tag yet) now supports Delphi XE6 and XE5, and ahost of older Delphi versions. Binary downloads are available at Download | GExperts
These were the release news items:
In addition to what is in those items, 1.37contain a substantial speed improvement and some other fixes from me (I hope this fix also will get in later) in the Grep Search.
It is likely that this will be the last GExperts that support Pre-Delphi-2007 versions (currently 2006, 2005, 8.02, 7.1 and 6.02).
It is not clear if there will be a GExperts for Appmethod, as Appmethod does not provide functioning command-line compilers like I already blogged about in Spring4D now has projects for Appmethod, but it cannot support Appmethod in the automated build engine.
You can get an Experimental GExperts version for Delphi XE6..6.02 (that includes a source formatter) from Experimental GExperts Version » twm’s blog.
From Thomas Mueller (the author of the experimental GExperts versions), there are also a few other interesting blog posts you probably will like:
- Determine the Delphi installation directory from a batch file » twm’s blog.
- Experimental GExperts Version 1.37-2014-04-16 released » twm’s blog.
- Experimental GExperts Version 1.37-2014-04-12 released » twm’s blog which is interesting because it shows you how to install GExperts when there is no official installer for it yet. An alternative is to use the batch files that are in my GExperts downloads page. Note I am working on a continuous integration server that will build a couple of open source Delphi projects (the plan is to include GExperts, DUnit and a few others) that makes it easier to publish those builds.
- Another way to install GExperts is by calling rundll322, as seen in change 860 and posted on Thomas Mueller – Google+ – I have just added code to the GExperts dll so it can…. Way easier than my batch files.
- Windows advanced Batch programming call :bla%var% » twm’s blog which is based on switch statement equivalent in Windows batch file – Stack Overflow.
–jeroen
via: Download | GExperts.
Share this:
Posted in Appmethod, Delphi, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 6, Delphi 7, Delphi 8, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Delphi XE5, Delphi XE6, Development, Software Development | Tagged: GExperts | 6 Comments »
delphi: idioms for building strings (via: my answer on Stack Overflow)
Posted by jpluimers on 2014/04/16
Once every while, one of your StackOverflow answers gets an edit suggestion that is really valuable.
This case it was Edwin Yip who suggested to emphasize the difference between TStringBuilder and TStringList (adding characters versus lines).
Too bad that freshly 10k user Makoto showed he hates bold emphasis, intentional property casing and post signatures by removing the added value (there is so much emphasis he could remove on other answers to warrant at least a day time job).
I know that not all emphasis is welcomed at StackOverflow, but in this case I think it added real value.
So I edited my own answer to add even more value: showing the idioms I use for building strings, and now it is time to quote it: Read the rest of this entry »
Share this:
Posted in Delphi, Delphi 1, Delphi 2, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi x64, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Development, Software Development | Leave a Comment »
Delphi `TParser` links
Posted by jpluimers on 2014/03/25
I needed to modify some code that had been amended from the Delphi TParser class (which parses DFM files, but can be amended to other sources as well), so here are some links I found during my research:
- CodeToHTML parser (with really nice flow diagrams).
- What is this TParser thing and how do I use it?.
- System.Classes.TParser – RAD Studio API Documentation.
- Brain := TBrain.Create(Head);: TParser в Delphi.
- Ray Lischner on TParser.
Oh and it is on the Delphi VCL Hierarchy poster too (:
–jeroen
Share this:
Posted in Delphi, Delphi 1, Delphi 2, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi x64, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Delphi XE5, Development, Software Development | Tagged: Delphi TParser | 2 Comments »
WITH IS EVIL! (via: Paul Foster – Google+)
Posted by jpluimers on 2014/03/13
Yet another example of somehow who got bitten hard by using the with statement (I decided to give with its own category on my blog).
This time it got shared by Paul Foster on G+ and comes down to this:
Even in unsuspiciously looking code, the wit statement can bite you, especially if you need to do refactoring and (because of that) introduce two names in the same scope.
Or in Paul‘s words:
Whilst upgrading the code to remove the Containers unit (its not supported on NextGen platforms, so I have to make things work with Generics.Collections instead, (bye bye D7 support for this code) and refactor a couple stupidities in my original design (they always creep in, don’t they) I ended up with two class members of the same name. The with block then looked OK but I was in fact not access the member I thought I was.
–jeroen
via: Paul Foster – Google+ – WITH IS EVIL! God damn it, I know it makes code easier to….
Share this:
Posted in Borland Pascal, Delphi, Delphi 1, Delphi 2, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi x64, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Delphi XE5, Development, Pascal, Software Development, Turbo Pascal, With statement | 18 Comments »
Delphi/Turbo Pascal: AppendWithRetry for text files to retry Append
Posted by jpluimers on 2014/03/10
Every once in a while you have multiple threads or processes wanting to write a short message to the same log file. Append then will give you an I/O error 32 (ERROR_SHARING_VIOLATION), but the below small routine will sleep a bit while retrying a couple of times.
It uses these Delphi aspects around the $I or $IOCHECKS compiler directive:
- in $I+ mode, you get exceptions when certain “classic” Pascal style I/O operations fail.
- in $I- mode, you access the IOResult to obtain the results of those I/O operations
- IOResult gets the result of the last failed operation (if any) or zero if none failed
- IOResult clears the underlying storage to zero
- $IFOPT checks for a certain state of a compiler flag
- You can store the state of $OPT in a temporary conditional define
Note there are a few tables of codes you can get back through IOResult as basically you can get many GetLastError results in IOResult as well: Read the rest of this entry »
Share this:
Posted in Delphi, Delphi 1, Delphi 2, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi x64, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Delphi XE5, Development, Software Development | 2 Comments »
Delphi types that cannot be used for TypeInfo
Posted by jpluimers on 2014/03/03
When writing the Spring4D unit tests for GetTypeSize to include as many TTypeKind values, I came across a few types that either did not compile, or were not supported by TypeInfo. I listed them below as I could not find them in the documentation.
I included a test named Test_EnsureAllTTypeKindsCoveredByCallsTo_Test_GetTypeSize_ that verifies that all TTypeKind values except tkUnknown are covered. So future extensions of TTypeKind will make the tests fail.
As a side issue, I really wanted to know if tkUnknown could be emitted by the compiler. It can sort of, for instance by defining discontiguous enumerations, but are incompatible with TypeInfo as well.
Types that do not compile at all: Read the rest of this entry »
Share this:
Posted in Agile, Delphi, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 8, Delphi x64, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Delphi XE5, Development, DUnit, Software Development, Unit Testing | 2 Comments »
Delphi: the Factory Pattern with virtual Create Constructors (via: What Design Patterns do you implement in common Delphi programming? – Stack Overflow)
Posted by jpluimers on 2014/02/20
Delphi Component Design
From long ago, but still very valid, as I recently had another question like “what design patterns does Delphi use?”.
The Delphi usage of patterns to make the VCL and your applications work is one of the reasons I like the Delphi Component Design: Danny Thorpe so much.
Do not let you scare by the book title: a lot of information in this book is much broader than designing components.
It is about why and how things are done in the RTL and VCL, and which patterns you can use yourself.
Try and git it while you can still get it. It is excellent, but rare to get as it has been out of print for a while.
Only a minority of the Delphi developers knows that every Delphi developer uses a Factory pattern (delphi.about.com has an example in “regular” Delphi), but then implemented using virtual Create constructors.
So: time to shed some light on that :-)
Virtual constructors are to classes like virtual methods are like object instances.
The whole idea of the factory pattern is that you decouple the logic that determines what kind (in this case “class”) of thing (in this case “object instance”) to create from the actual creation.
It works like this using virtual Create constructors:
TComponent has a virtual Create constructor so, which can be overridden by any descending class:
type TComponent = class(TPersistent, ...) constructor Create(AOwner: TComponent); virtual; ... end;For instance the TDirectoryListBox.Create constructor overrides it:
type TDirectoryListBox = class(...) constructor Create(AOwner: TComponent); override; ... end;You can store a class reference (the class analogy to an object instance reference) in a variable of type ‘class type’. For component classes, there is a predefined type TComponentClass in the Classes unit:
type TComponentClass = class of TComponent;When you have a variable (or parameter) of type TComponentClass, you can do polymorphic construction, which is very very similar to the factory pattern:
var ClassToCreate: TComponentClass; ... procedure SomeMethodInSomeUnit; begin ClassToCreate := TButton; end; ... procedure AnotherMethodInAnotherUnit; var CreatedComponent: TComponent; begin CreatedComponent := ClassToCreate.Create(Application); ... end;The Delphi RTL uses this for instance here:
Result := TComponentClass(FindClass(ReadStr)).Create(nil);and here:
// create another instance of this kind of grid SubGrid := TCustomDBGrid(TComponentClass(Self.ClassType).Create(Self));The first use in the Delphi RTL is how the whole creation process works of forms, datamodules, frames and components that are being read from a DFM file.
The form (datamodule/frame/…) classes actually have a (published) list of components that are on the form (datamodule/frame/…). That list includes for each component the instance name and the class reference.
When reading the DFM files, the Delphi RTL then:
- finds about the components instance name,
- uses that name to find the underlying class reference,
- then uses the class reference to dynamically create the correct object
A regular Delphi developer usually never sees that happen, but without it, the whole Delphi RAD experience would not exist.
Allen Bauer (the Chief Scientist at Embarcadero), wrote a short blog article about this topic as well.
There is also a SO question about where virtual constructors are being used.Let me know if that was enough light on the virtual Create constructor topic :-)
–jeroen via: What Design Patterns do you implement in common Delphi programming? – Stack Overflow.
Share this:
Posted in Delphi, Delphi 1, Delphi 2, Delphi 2005, Delphi 2006, Delphi 2007, Delphi 2009, Delphi 2010, Delphi 3, Delphi 4, Delphi 5, Delphi 6, Delphi 7, Delphi 8, Delphi x64, Delphi XE, Delphi XE2, Delphi XE3, Delphi XE4, Delphi XE5, Development, Software Development | Tagged: Delphi, Delphi Component Design | 4 Comments »
The Wiert Corner - irregular stream of stuff 