I downloaded the OTL http://www.omnithreadlibrary.com/
and compile the D2007 grouproj, install the package, without problem.
I then create a simple console application that uses OtlParallel unit, of course, I add the OtlParallel and some other pas files to the project.
But it complains that Generics.Collections is not found.
The documentation says:
High-level abstractions are implemented in the OtlParallel unit. They are all created through the factory class Parallel. High-level code intensively uses anonymous methods and generics which makes Delphi 2009 the minimum supported version.
This us of both generics and anonymous methods makes this unit completely incompatible with Delphi 2007.
If you wish to use a construct like Parallel.For with Delphi 2007 and OTL then you will have to back-port OtlParallel yourself. Without anonymous methods this is very difficult to do and achieve the same fluid style of code. You would have to use procedural types instead of anonymous methods. And you would have to implement closures manually.
So instead of using
TProc = reference to procedure;
you would use
TMethod = procedure of object;
And then to implement this you create a class or record with a parameterless method. You'll need to add whatever state is needed as members of the type, and populate those members. That is in essence a manual implementation of a closure with variable capture. And you'll need to deal with lifetime. Make sure that the instances outlive the parallel loop.
Good luck!
Related
I'm currently struggling with the following:
I need to create two different DLL's, which do exactly the same but are looking to a different DB. The two DB's are nothing alike.
My dll's should be handling the communication with those different DB's.
So that the main program chooses which dll he wants to use.
I want to be sure each dll has exactly the same procudes/functions/...
I was thinking of using interfaces.
But I can't figure out how to create global interfaces. the dll's belong to the same projectgroup.
I do believe you're making a "mountain out of a molehill" thinking you need 2 different DLLs. But if you choose the last of my suggested options, you should find it fairly easy to switch between a 2 DLL solution and 1 DLL solution.
Option 1
This is the most straightforward:
Create a new unit.
Add your DLL interface (the exports).
Include the unit in both projects.
unit DllExportIntf;
interface
uses
DllExportImpl;
exports DoX;
implementation
end.
Note that this unit uses DllExportImpl which will also have to be included in both projects. However, you'll need 2 different files with the same name in 2 different locations in your file system. So each DLL project will have different implementations.
Now whenever you make a change to your interface, your projects won't compile until you've updated each of the DllExportImpl units.
What I don't particularly like about this solution is the need for units with the same name but different behaviour. Since you intend having both DLLs in the same project group: I should warn you that I've experienced the IDE getting confused by duplicate unit names.
Option 2
Place the exports into a shared include file.
library DllSharedExportsImpl1;
uses
DllExportImpl1 in 'DllExportImpl1.pas';
{$I ..\Common\DllExports.inc}
The DllExports.inc file will only include your exports clauses. E.g.
exports DoX;
This has the advantage that now each DLL can use different unit names for the different implementations. And if you change your include file, neither project will compile until you've updated its implementation unit to accommodate the change.
Note that this does come with its own set of problems. The way includes work: the compiler effectively shoves the contents of the include file into the unit at compile time. So what looks like line 7 to the IDE is entirely different to the compiler. Also editing include files can be a bit of a nuisance because context can only be determined where the file is included making editor support quite impractical.
Option 3
This option is a little more work, but provides much better long-term maintainability.
You do this by implementing your interface via polymorphic objects. In this way, both DllProjects will also share the routines that are actually exported. When each DLL initialises, it sets the concrete implementation to be used.
Your DLL interface could look something like this.
unit DllExportIntf;
interface
type
TAbstractImpl = class(TObject)
public
procedure DoX; virtual; abstract;
end;
procedure AssignDllImpl(const ADllImpl: TAbstractImpl);
procedure DoX;
exports DoX;
implementation
var
GDllImpl: TAbstractImpl;
procedure AssignDllImpl(const ADllImpl: TAbstractImpl);
begin
if Assigned(GDllImpl) then
begin
GDllImpl.Free;
end;
GDllImpl := ADllImpl;
end;
procedure DoX;
begin
GDllImpl.DoX;
end;
end.
When you initialise your DLL, you can call:
AssignDllImpl(TDllImpl_1.Create);
A clear advantage of this approach is that if there is any common code between your 2 DLLs, it can be included in your base implementation. Also, if you can change an existing method DLL in such a way that it does not require a change to TAbstractImpl, you possibly will only need to recompile your DLLs.
Furthermore, if you need to change existing virtual abstract methods, you will have to update the overrides in your concrete implementations accordingly.
WARNING If you add a new virtual abstract method, your projects will still compile with warnings that you are creating objects with abstract methods. However, you should always treat warnings as errors. If you do, this caveat won't be a problem.
NOTE: As mentioned earlier, using this approach you should be able to fairly easily switch between single DLL and 2 DLL solutions. The difference basically boils down to which units are included in the project, and how you initialise the global.
It may also be worthwhile mentioning that you could even eliminate the global altogether by implementing a Handle to use with each of your DLL routines. (Similar to Windows.) Bear in mind that there are technical issues when trying to pass objects between DLL and application code. This is why instead of passing objects, you use a "handles" to objects and encapsulate the actual object instances internally.
Considering all that was said, I believe that you would be more successful if you design your solution with packages, not DLLs. A package is a DLL, but rich in symbols, so Delphi can be a better use of it. Particularly, the symbols declared inside the package will more easily be loaded by your application, with a much higher level of abstraction. It´s what the Delphi IDE uses to load components.
So, following this design, this is what you have to do:
Declare your interfaces in units existing in a package named (for instance) DBServices.dpk. Here is an example of such an unit:
unit DBService1;
interface
uses
....;
type
IService1 = interface
[....] // here goes the GUID
procedure ServiceMethod1;
procedure ServiceMethod2;
// and so on...
end;
implementation
end.
So, above you created an unit that declares an interface. Your aplication can use that interface anywhere, just reference the package in your application and use it in other units and you will have the access to the symbols declared.
Declare the implementation class for that very same interface in another unit of another package, for instance, dedicated to SQLServer (SQLServerServices.dpk):
unit SQLServerService1;
interface
uses
DBService1, ....;
type
TSQLServerService1 = class(TInterfacedObject, IService1)
protected // IService1
procedure ServiceMethod1;
procedure ServiceMethod2;
// and so on...
end;
implementation
procedure TSQLServerService.ServiceMethod1;
begin
// Specific code for SQL Server
end;
procedure TSQLServerService.ServiceMethod2;
begin
// Specific code for SQL Server
end;
...
end.
Above you declared an implementing class for the interface IService1. Now you have two packages, one declaring the interfaces and other implementing those interfaces. Both will be consumed by your application. If you have more implementations for the same interfaces, add other packages dedicated to them.
One important thing is: you have to have a factory system. A factory system is a procedure ou class that will create and return the implementations for your application from each package.
So, in terms of code, in each service package (the ones that implement the interfaces) add a unit named, for instance, xxxServiceFactories, like this:
unit SQLServerServiceFactories;
interface
uses
DBService1;
function NewService1: IService1;
implementation
uses
SQLServerService1;
function NewService1: IService1;
Result := TSQLServerService1.Create;
end;
end.
The code above declares a function that creates the SQL Server implementation and returns it as an interface. Now, if you call a method from the interface returned, you will be actually calling the specific implementation of it for SQL Server.
After loading the package, you will have to link to that function in the very same way you would do if working if a DLL. After you have the pointer for the function, you can call it and you will have the interface in your application's code:
...
var
service1: IService1;
begin
service1 := NewService1;
service1.ServiceMethod1; // here, calling your method!
end;
The model I described in this answer is the one I used in a similar scenario I had to deal with in the past. I presented general ideas that work, but you have to understand the fundamentals of packages and interfaces to really master the technique.
A comprehensive explanation on those matters would be very long for an answer here, but I guess it will be a good starting point for you!
What you want to do is create a COM component project. Define your methods on that & implementations for one DB. Then create a second COM component that uses the same interface.
On the off-chance that your question is more about the fundamentals of Delphi, I've added another answer which may be more helpful to you than the first one. My first answer focused on getting 2 DLLs to expose the same methods (as per the main body of your question). This one focuses on the last 2 sentences of your question:
But I can't figure out how to create global interfaces. The dll's belong to the same project group.
Based on this, it sounds like you're looking for an option to "mark an interface as global so that projects in the same group can use them". Delphi doesn't need a special feature to do this because it's trivially available if you understand certain fundamental principles.
When you create a new unit, it is by default added to the current project. However if you want to share the unit between multiple projects, it's a good idea to save it to a different folder so it's easy to see that it's shared. Your first DLLs project file should look something like this.
library Dll1;
uses
DllSharedIntf in '..\Common\DllSharedIntf.pas';
You can define your "global" interface in the DllSharedIntf unit. E.g.
unit DllSharedIntf;
interface
type
IDllIntf = interface
['{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}']
procedure DoX;
end;
implementation
end.
NOTE: Because the interface type is declared in the interface section of the unit, it is considered "global" because other units are able to use it. But this doesn't automatically make it available to other projects.
You now have to add the shared unit to your other project so it becomes available for use by other units in that project. To do this:
Activate Dll2
Select Project and Add to Project...
Find DllSharedIntf and add it.
Delphi will automatically update your project source file to include the unit.
library Dll2;
uses
DllSharedIntf in '..\Common\DllSharedIntf.pas';
Now in each DLL project you can add a separate implementation unit. E.g. For Dll1:
unit DllImpl1;
interface
uses
//It's very important to indicate that this unit uses the shared unit.
//Otherwise you won't be able to access the "global types" declared
//in the interface-section of that unit.
DllSharedIntf;
type
TDllImpl1 = class(TInterfacedObject,
//Any types defined in the interface-section of any units that
//this unit **uses**, can be accessed as if they were declared
//in this unit.
IDllIntf)
protected
//The fact that this class is marked as implementing the IDllIntf
//means that the compiler will insist on you implementing all
//methods defined in that interface-type.
procedure DoX;
end;
implementation
NOTE This answer only covers sharing an interface between projects. You'll still need to expose the functionality of the DLLs via appropriate exports. You'll need an approach similar to option 3 of my other answer.
Summary
We don't usually talk about "global interfaces" in Delphi. It's generally understood that anything declared in the interface section of a unit is globally accessible. (We do make more of an issue about global variables due to their dangers though; but that's an entirely different topic.)
In Delphi:
Whenever you want one unit (A) to make use of functionality defined in another unit (B), you need to add unit B to the uses clause of unit A.
Whenever you want a project to use a unit created in another project, you need to add the unit to the project. (TIP: It's a good idea to put such units in a separate folder.)
NOTE: When sharing units between projects, the project group is actually irrelevant. Projects don't need to be in the same group to share units. All you need to do is ensure the project can access the unit so that other units in your project can uses it.
I'm trying to figure out a safe way of passing objects from a main app to a DLL (for a plugin system).
The idea is to use the main app's TZConnection (database access from Zeos Lib) in the dll's.
I'd rather not use Runtime Packages, and DLL must be the way to go (I don't need BPL's need to recompile each time, and have no idea of how to use COM).
I've been told it's possible to do it with Interfaces.
I've never used them before, but been messing around with it, and managed to do it... But, I don't know if I did it right (as in, safe).
Here's my Interface unit.
unit PluginIntf;
interface
uses
ZConnection, ZDataSet;
type
IQueryResult = interface ['{743AB77E-7897-403E-A0D9-4D02748E565D}']
function GetRecordCount: Integer;
function GetDataSet: TZQuery;
end;
IPluginHost = interface ['{A5A416B4-437E-4A1E-B228-0F94D54840B0}']
function RunSql(const SQLString:WideString): IQueryResult;
end;
IPlugin = interface ['{8D9591C3-5949-4F0A-883E-6ABD02597846}']
function GetCaption: WideString;
end;
implementation
end.
In IQueryResult, I'm passing a TZQuery. It works, but... Is it safe?
Is there any other way to wrap it in the Interface?
Thank you
Nuno Picado
TZQuery is a class. Therefore it is not safe to pass one across the module boundary unless you use runtime packages. Use a class with DLLs and you actually have two separate types, one in each module.
You are correct that interfaces are safe for this but you need to restrict yourself to DLL interop safe types. That is simple types, records, pointers to arrays, interfaces, or combinations of these types.
You need to wrap TZQuery with an interface that exposes it's functionality.
I'm trying to create a shell extension to provide EXIF information for JPEG files in Windows Explorer "infotips", and am using Lazarus as this needs to produce an x64 DLL.
Does Lazarus support multiple inheritance with interfaces, and if so, how do I go about it?
for example, something like:
type
IInfoTips = interface(IPersistFile, IQueryInfo)
Thanks,
Mark
No, interfaces in FPC does not support multi-inheritance yet.
What you can do is letting the implementation class inherit from both interfaces:
type
TMyInfoTips = class(TInterfacedObject, IPersistFile, IQueryInfo)
But not at interface level, as you wish. Such statements won't compile:
type
IInfoTips = interface(IPersistFile, IQueryInfo)
You can only "inherit" from a single interface type.
Delphi does not support it either. Only the defunct Delphi for .Net compiler did... but because .Net/C# IR supports (and expects) the feature.
I'm also missing this feature in Delphi or FPC.
Both interfaces are defined in shlobj for Free Pascal/Lazarus, just like on Delphi. If symbols changed units during the Delphi lifetime, we try to put them in the more recent units, but there is a large backlog there.
All this should be largely Delphi compatible, maybe it is easier if you explained what exactly doesn't work like expected.
Added after Arnaud's comments:
No it does not. Objects implement interfaces in Pascal. I don't really understand why it is really important to do this anyway. Sure it is a bit of syntactic sugar, but since any delphi style interface implements Iunknown, you can just query an interface for another interface:
uses activex;
var x :IPersistfile;
y :IPersistStream;
begin
x.queryinterface(IID_IPersistStream,y);
end.
Is it possible to let the IDE automatically implement inherited abstract methods in Delphi XE? In Java and C# IDEs it's a common functionality like pressing ALT+SHIFT+F10 in Visual Studio or ALT+RETURN in IntelliJ IDEA.
Without this I always have to look up manually which methods have to be implemented and copy their declarations, which really is something I shouldn't have to do nowadays!
You can use ctrl+space in the class declaration to get a list of all the methods you might want to override (or implement from an interface). It does however not tell you which is abstract but once you figured that out you will get the declaration for free by selecting the method(s) from the list.
And after that you can of course use class completion ctrl+shift+c to generate the code in implementation section.
No, the Delphi IDE doesn't have an automatic shortcut for this. But, you can use the compiler to make it easier on you.
Define your new class. Then put a line somewhere in your code that says TMyNewClass.Create(whatever). When the compiler parses this, if there are any unimplemented abstract methods on TMyNewClass, it will tell you about them in the compiler warnings.
I'm attempting to write a unit test for a simple factory class that creates one of several possible implementing objects and returns it as an interface reference.
DUnit has a built in procedure, CheckIs(AObject: TObject; AClass: TClass; msg: string), that based on its name and the parameters it accepts should fail the test if the object's class type doesn't match the expected one. The only problem is it requires an object reference not an interface reference.
So I'm trying to use CheckTrue and perform the comparison in the body of the test but I'm not as familiar with Delphi's type checking support as I am with C#'s.
I know the is operator is out of the question since it only works with object references.
CheckTrue(LMyInterfaceReference {comparison here} TMyClass);
Any suggestions?
BTW, I'm using Delphi 2009 so I don't have access to the new RTTI support added in 2010+.
I'm wondering why you MUST have to test this... maybe you really don't have to.
But if knowing the underlying object of a Interface is a must, you have two choices:
Add a method to the interface which returns the underlying object, just a TObject, and implement this in each class just by returning self.
Hack a bit, for example using this Interface to object routine.
If you don't like hacks and don't feel like upgrading to Delphi 2010+ you may use an interface like this:
IImplementingObjectInterface = interface
function GetImplementingObject: TObject;
end;
Make sure your objects also implement this interface and use it to extract the implementing object. If you need to do this for a lot of objects you can define your own TInterfacedObject derivate that already implements this so you can simply change your inheritance and be done.
Barry Kelly (one of the main Embarcadero Delphi Compiler Engineers) wrote a nice An ugly alternative to interface to object casting this week.
It answers your question.
The fun is that Hallvard Vassbotn wrote a very similar piece of code back in 2004.
From Delphi 2010 on, you can just use an is check or as cast to go back from interface references to object references.
--jeroen