Posted by jpluimers on 2020/10/07
I see lots of code using abbreviations. Please avoid those, just like many development stacks urge you to do so.
Two important reasons:
This is not limited to the software development field; for similar reasons, the medical field also limits the use of abbreviations and acronyms:
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Posted by jpluimers on 2020/09/30
A feature overlooked by many Delphi programmer was already introduced in Delphi 1 which is more or less the same as in the Delphi 2007 documentation at [WayBack] Type Compatibility and Identity.
There is a distinction between these explained in the above link:
type TMyInteger1 = Integer; TMyInteger2 = type Integer;
Where TMyInteger1 is an alias for Integer, TMyInteger2 introduces a new type which is distinct from Integer and TMyInteger. That way the compiler can set them apart, and even generates separate RTTI (Run-Time TypeInformation) for them.
Probably the most used distinct types are these:
TDateTime = type Double;
...
TDate = type TDateTime;
TTime = type TDateTime;
TFontName = type string
These are unlike TColor which is defined as “just” a subrange of Integer, but because it is a subtype, also gets a distinct type:
TColor = -$7FFFFFFF-1..$7FFFFFFF;
Type identity is important because Delphi 1 introduced these mechanisms:
Without them, very basic Delphi features would not work.
In addition, a lot of other RTTI based code now enables features like object relational mapping, binding to JSON/XML and many others.
What I did not know is that the Pascal and Delphi type systems have been heavily influenced by ADA. Luckily Lutz Donnerhacke pointed me to ADA [WayBack] Types and Subtypes.
I made an example Distinct type types in Delphi · GitHub showing the differences on RTTI level in these properties:
property IntegerProperty: Integer read FIntegerField write FIntegerField;
property ColorProperty: TColor read FColorField write FColorField;
property DoubleProperty: Double read FDoubleField write FDoubleField;
property DateTimeProperty: TDateTime read FDateTimeField write FDateTimeField;
property DateProperty: TDate read FDateField write FDateField;
property TimeProperty: TTime read FTimeField write FTimeField;
property StringProperty: string read FStringField write FStringField;
property FontNameProperty: TFontName read FFontNameField write FFontNameField;
The generated table (see also the source below using [Archive.is] TRttiContext added in Delphi 2010) indeed shows distinct types on the RTTI level:
NameType.NameType.QualifiedNameType.TypeKindIntegerPropertyIntegerSystem.IntegertkIntegerColorPropertyTColorSystem.UITypes.TColortkIntegerDoublePropertyDoubleSystem.DoubletkFloatDateTimePropertyTDateTimeSystem.TDateTimetkFloatDatePropertyTDateSystem.TDatetkFloatTimePropertyTTimeSystem.TTimetkFloatStringPropertystringSystem.stringtkUStringFontNamePropertyTFontNameSystem.UITypes.TFontNametkUString
This post was inspired by an interesting discussion on [WayBack] What’s the technical term for the following construct: type intx = type integer; type inty = integer; What term would you use to describe the differen… – Johan Bontes – Google+
Documentation:
RTTI dump inspired by [WayBack] delphi – How can I distinguish TDateTime properties from Double properties with RTTI? – Stack Overflow.
–jeroen
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Posted by jpluimers on 2020/09/30
I have summarised the main topics of each part in this table of contents, and indicated at the time of writing which parts I did not get yet:
Via: [WayBack] So You Want to be a Functional Programmer (Part 1) Link to part 2 in the article. https://medium.com/@cscalfani/so-you-want-to-be-a-functional-programm… – Lars Fosdal – Google+
–jeroen
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Posted by jpluimers on 2020/09/23
As of Delphi XE6, the VCL also styles non-VCL controls, but this truncates the texts to 256 characters, for instance in non-balloon hints. This is fixed in Delphi 10.2 Berlin, by making the buffer dynamic and switching obtaining those texts from using GetWindowText to sending a WM_GETTEXT message.
A fix for Delphi XE6..10.1 Berlin is at gitlab.com/wiert.me/public/delphi/DelphiVclStylesAndHintText, with many thanks to Stefan Glienke who based the patch on the ones used in Spring4D. I think they are similar to the ones in [Archive.is] VCL Fix Pack 1.4 | Andy’s Blog and Tools.
The Old New Thing explains the difference between GetWindowText and WM_GETTEXT in [WayBack] The secret life of GetWindowText – The Old New Thing. TL;DR:
GetWindowText strikes a compromise.
- If you are trying to GetWindowText() from a window in your own process, then GetWindowText() will send the WM_GETTEXT message.
- If you are trying to GetWindowText() from a window in another process, then GetWindowText() will use the string from the “special place” and not send a message.
So for your own process, it does not matter as GetWindowText uses WM_GETTEXT.
–jeroen
Related:
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Posted by jpluimers on 2020/09/22
A nice thread with examples of all the things you should not do with the Delphi reintroduce keyword:
[WayBack] Delphi Gem of the day: putting “reintroduce” on a destructor. destructor Destroy(); reintroduce; overload; In our case all we got was a memory lea… – Moz Le – Google+
The problem is that in the original (archived) documentation, not much waring is given around using reintroduce; it is merely posted as solving a nuisance to absolve a compiler warning.
When using it though, all your alarm systems should go off at their highest level as you break polymorphism, but through careful language usage, the pattern you hide can still be used.
One day I will write a longer blog article on this.
Documentation:
A decade of progress has not changed much on this documentation apart from some nicer formatting:
–jeroen
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Posted by jpluimers on 2020/09/17
A while ago, I needed the opposite of InvRegistry.RegisterInterface(TypeInfo(MySoapInterfacePortType, 'urn:myURN', 'utf-8');, so instead of registering an interface with a namespace URN, obtain the URN by passing the interface inverting [WayBack] TInvokableClassRegistry.RegisterInterface.
This is the class helper I wrote:
type
TInvokableClassRegistryHelper = class helper for TInvokableClassRegistry
public
function GetInterfaceNamespace(Info: PTypeInfo): string;
end;
function TInvokableClassRegistryHelper.GetInterfaceNamespace(Info: PTypeInfo): string;
var
InfoGuid: TGUID;
begin
// call like `Result := InvRegistry.GetInterfaceNamespace(TypeInfo(MySoapInterfaceType));`
InfoGuid := GetTypeData(Info)^.Guid; // uses TypInfo; see https://stackoverflow.com/questions/8439246/is-it-possible-to-get-the-value-of-a-guid-on-an-interface-using-rtti
Result := GetNamespaceByGUID(InfoGuid);
end;
It would have been a lot easier if TInvokableClassRegistry.GetIntfIndex has been public, because then [WayBack]TInvokableClassRegistry.GetRegInterfaceEntry could have been used.
–jeroen
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Posted by jpluimers on 2020/09/11
The Delphi WSDL importer maintenance has been in dormant mode for a long while, which means it still barfs on WSDL include directives.
In the day and age of REST and gRPC, I don’t think it will get any love soon.
Related bug entries are for instance RSP-18630: WSDL generate bad code and RSP-17321: “Import WSDL” generates invalid code without explanation of problem are examples of this, and I’m sure that QC had more if it were still alive; I could find these in the WayBack machine:
The problem manifests itself when the WSDL file includes one or more XSD files. The generated code will contain a section like this:
// ************************************************************************ // // The following types, referred to in the WSDL document are not being represented // in this file. They are either aliases[@] of other types represented or were referred // to but never[!] declared in the document. The types from the latter category // typically map to predefined/known XML or Embarcadero types; however, they could also // indicate incorrect WSDL documents that failed to declare or import a schema type. // ************************************************************************ //
Further below is a series of commented out types, all starting with a ! end ending in a column with the namespace of those types.
Searching for the first line gives numerous examples as far back as Delphi 7, for instance:
Based on those, I think the reason is that the WSDL importer fails on <soap:binding transport="http://schemas.xmlsoap.org/soap/http" style="document" /> which is quite common in the real world.
I did not want to pursue manually modifying the WSDL file, or manually generating the types as the WSDL and XSD files were prone to changes and manual steps would make the re-import process more tedious. If you do want to do that, these link might help:
This is what I used to get this to compile and run [WayBack] Web Service Toolkit – Free Pascal wiki:
Associate .inc files with FreePascal IDEC:\FPC\3.0.4\bin\i386-win32 to the user pathwst-0.7u directoryws_helper subdirectoryWhen compiling in Delphi, then you definitely need the FreePascal RTL sources for the PasTree unit; see [WayBack] fcl-passrc – Free Pascal wiki.
Related:
–jeroen
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Posted by jpluimers on 2020/09/09
Recursion explained visually.
Via [WayBack] Wenn mehrere Generationen in den Feiertag / Vatertag starten.
[WayBack] Original picture at [WayBack] Bug Life | Chickie’s Rides | Pinterest | Vw, Volkswagen and Cars.
–jeroen
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Posted by jpluimers on 2020/08/31
From an interesting thread at [WayBack] What’s the piece of Delphi knowledge you find yourself looking up over and over again? For me format strings is probably the thing that most stubbornly… – Lachlan Gemmell – Google+
On the generics side, I have wrote a few bits in my blog before, often pointing to information by others (many by Stefan Glienke as his skills on this topic are beyond excellent):
And on records:
There are some very good books on Delphi though that dig deeper than the documentation:
–jeroen
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Posted by jpluimers on 2020/08/25
In addition to Shared/IShared, there is also Weak/IWeakReference in Spring.pas; these blog post explain more about them:
{$REGION 'Shared smart pointer'} at the current repository):
{$REGION 'Weak smart pointer'} at the current repository):
Related: If you were using Managed / IManaged in Spring4D, be aware they got renamed to Shared / IShared.
–jeroen
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The Wiert Corner - irregular stream of stuff 