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  • Delphi RTTI unable to find interface

    - by conciliator
    I'm trying to fetch an interface using D2010 RTTI. program rtti_sb_1; {$APPTYPE CONSOLE} {$M+} uses SysUtils, Rtti, mynamespace in 'mynamespace.pas'; var ctx: TRttiContext; RType: TRttiType; MyClass: TMyIntfClass; begin ctx := TRttiContext.Create; MyClass := TMyIntfClass.Create; // This prints a list of all known types, including some interfaces. // Unfortunately, IMyPrettyLittleInterface doesn't seem to be one of them. for RType in ctx.GetTypes do WriteLn(RType.Name); // Finding the class implementing the interface is easy. RType := ctx.FindType('mynamespace.TMyIntfClass'); // Finding the interface itself is not. RType := ctx.FindType('mynamespace.IMyPrettyLittleInterface'); MyClass.Free; ReadLn; end. Both IMyPrettyLittleInterface and TMyIntfClass = class(TInterfacedObject, IMyPrettyLittleInterface) are declared in mynamespace.pas. Do anyone know why this doesn't work? Is there a way to solve my problem? Thanks in advance!

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  • How to create an instance of object with RTTI in Delphi 2010?

    - by Paul
    As we all known, when we call a constructor of a class like this: instance := TSomeClass.Create; The Delphi compiler actually do the following things: Call the static NewInstance method to allocate memory and initialize the memory layout. Call the constructor method to perform the initialization of the class Call the AfterConstruction method It's simple and easy to understand. but I'm not very sure how the compiler handle exceptions in the second and the third step. It seems there are no explicit way to create an instance using a RTTI constructor method in D2010. so I wrote a simple function in the Spring Framework for Delphi to reproduce the process of the creation. class function TActivator.CreateInstance(instanceType: TRttiInstanceType; constructorMethod: TRttiMethod; const arguments: array of TValue): TObject; var classType: TClass; begin TArgument.CheckNotNull(instanceType, 'instanceType'); TArgument.CheckNotNull(constructorMethod, 'constructorMethod'); classType := instanceType.MetaclassType; Result := classType.NewInstance; try constructorMethod.Invoke(Result, arguments); except on Exception do begin if Result is TInterfacedObject then begin Dec(TInterfacedObjectHack(Result).FRefCount); end; Result.Free; raise; end; end; try Result.AfterConstruction; except on Exception do begin Result.Free; raise; end; end; end; I feel it maybe not 100% right. so please show me the way. Thanks!

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  • Converting an AnsiString to a Unicode String

    - by jrodenhi
    I'm converting a D2006 program to D2010. I have a value stored in a single byte per character string in my database and I need to load it into a control that has a LoadFromStream, so my plan was to write the string to a stream and use that with LoadFromStream. But it did not work. In studying the problem, I see an issue that tells me that I don't really understand how conversion from AnsiString to Unicode string works. Here is some code I am puzzling over: oStringStream := TStringStream.Create(sBuffer); sUnicodeStream := oPayGrid.sStream; //explicit conversion to unicode string iSize1 := StringElementSize(oPaygrid.sStream); iSize2 := StringElementSize(sUnicodeStream); oStringStream.WriteString(sUnicodeStream); When I get to the last line, iSize1 does equal 1 and iSize2 does equal 2, so that part is what I understood from my reading. But, on the last line, after I write the string to the stream, and look at the Bytes Property of the string, it shows this (the string starts as '16,159'): (49 {$31}, 54 {$36}, 44 {$2C}, 49 {$31}, 53 {$35}, 57 {$39} ... I was expecting that it might look something like (49 {$31}, 00 {$00}, 54 {$36}, 00 {$00}, 44 {$2C}, 00 {$00}, 49 {$31}, 00 {$00}, 53 {$35}, 00 {$00}, 57 {$39}, 00 {$00} ... I'm not getting the right results out of the LoadFromStream because it is reading from the stream two bytes at a time, but the data it is receiving is not arranged that way. What is it that I should do to give the LoadFromStream a well formed stream of data based on a unicode string? Thank you for your help.

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  • Delphi: how to set the length of a RTTI-accessed dynamic array using DynArraySetLength?

    - by conciliator
    I'd like to set the length of a dynamic array, as suggested in this post. I have two classes TMyClass and the related TChildClass defined as TChildClass = class private FField1: string; FField2: string; end; TMyClass = class private FField1: TChildClass; FField2: Array of TChildClass; end; The array augmentation is implemented as var RContext: TRttiContext; RType: TRttiType; Val: TValue; // Contains the TMyClass instance RField: TRttiField; // A field in the TMyClass instance RElementType: TRttiType; // The kind of elements in the dyn array DynArr: TRttiDynamicArrayType; Value: TValue; // Holding an instance as referenced by an array element ArrPointer: Pointer; ArrValue: TValue; ArrLength: LongInt; i: integer; begin RContext := TRTTIContext.Create; try RType := RContext.GetType(TMyClass.ClassInfo); Val := RType.GetMethod('Create').Invoke(RType.AsInstance.MetaclassType, []); RField := RType.GetField('FField2'); if (RField.FieldType is TRttiDynamicArrayType) then begin DynArr := (RField.FieldType as TRttiDynamicArrayType); RElementType := DynArr.ElementType; // Set the new length of the array ArrValue := RField.GetValue(Val.AsObject); ArrLength := 3; // Three seems like a nice number ArrPointer := ArrValue.GetReferenceToRawData; DynArraySetLength(ArrPointer, ArrValue.TypeInfo, 1, @ArrLength); { TODO : Fix 'Index out of bounds' } WriteLn(ArrValue.IsArray, ' ', ArrValue.GetArrayLength); if RElementType.IsInstance then begin for i := 0 to ArrLength - 1 do begin Value := RElementType.GetMethod('Create').Invoke(RElementType.AsInstance.MetaclassType, []); ArrValue.SetArrayElement(i, Value); // This is just a test, so let's clean up immediatly Value.Free; end; end; end; ReadLn; Val.AsObject.Free; finally RContext.Free; end; end. Being new to D2010 RTTI, I suspected the error could depend on getting ArrValue from the class instance, but the subsequent WriteLn prints "TRUE", so I've ruled that out. Disappointingly, however, the same WriteLn reports that the size of ArrValue is 0, which is confirmed by the "Index out of bounds"-exception I get when trying to set any of the elements in the array (through ArrValue.SetArrayElement(i, Value);). Do anyone know what I'm doing wrong here? (Or perhaps there is a better way to do this?) TIA!

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  • Delphi interface cast using TValue

    - by conciliator
    I've recently experimented extensively with interfaces and D2010 RTTI. I don't know at runtime the actual type of the interface; although I will have access to it's qualified name using a string. Consider the following: program rtti_sb_1; {$APPTYPE CONSOLE} uses SysUtils, Rtti, TypInfo, mynamespace in 'mynamespace.pas'; var ctx: TRttiContext; InterfaceType: TRttiType; Method: TRttiMethod; ActualParentInstance: IParent; ChildInterfaceValue: TValue; ParentInterfaceValue: TValue; begin ctx := TRttiContext.Create; // Instantiation ActualParentInstance := TChild.Create as IParent; {$define WORKAROUND} {$ifdef WORKAROUND} InterfaceType := ctx.GetType(TypeInfo(IParent)); InterfaceType := ctx.GetType(TypeInfo(IChild)); {$endif} // Fetch interface type InterfaceType := ctx.FindType('mynamespace.IParent'); // This cast is OK and ChildMethod is executed (ActualParentInstance as IChild).ChildMethod(100); // Create a TValue holding the interface TValue.Make(@ActualParentInstance, InterfaceType.Handle, ParentInterfaceValue); InterfaceType := ctx.FindType('mynamespace.IChild'); // This cast doesn't work if ParentInterfaceValue.TryCast(InterfaceType.Handle, ChildInterfaceValue) then begin Method := InterfaceType.GetMethod('ChildMethod'); if (Method <> nil) then begin Method.Invoke(ChildInterfaceValue, [100]); end; end; ReadLn; end. The contents of mynamespace.pas is as follows: {$M+} IParent = interface ['{2375F59E-D432-4D7D-8D62-768F4225FFD1}'] procedure ParentMethod(const Id: integer); end; {$M-} IChild = interface(IParent) ['{6F89487E-5BB7-42FC-A760-38DA2329E0C5}'] procedure ChildMethod(const Id: integer); end; TParent = class(TInterfacedObject, IParent) public procedure ParentMethod(const Id: integer); end; TChild = class(TParent, IChild) public procedure ChildMethod(const Id: integer); end; For completeness, the implementation goes as procedure TParent.ParentMethod(const Id: integer); begin WriteLn('ParentMethod executed. Id is ' + IntToStr(Id)); end; procedure TChild.ChildMethod(const Id: integer); begin WriteLn('ChildMethod executed. Id is ' + IntToStr(Id)); end; The reason for {$define WORKAROUND} may be found in this post. Question: is there any way for me to make the desired type cast using RTTI? In other words: is there a way for me to invoke IChild.ChildMethod from knowing 1) the qualified name of IChild as a string, and 2) a reference to the TChild instance as a IParent interface? (After all, the hard-coded cast works fine. Is this even possible?) Thanks!

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