DLL Exportiert ein Interface mit Strings...

[Sir Rufo]

Und hier mal komplett zusammengebaut:

• DLL
  
  Delphi-Quellcode:

  library dp_180689_lib;
  
  uses
    System.SysUtils,
    ExternalClassLibWrapper in 'ExternalClassLibWrapper.pas',
    ExternalClassIntf in 'ExternalClassIntf.pas',
    ExternalClass in 'lib\ExternalClass.pas';
  
  {$R *.res}
  
  function GetExternalClassWrapper : IExternalClassWrapper; safecall;
  begin
    Result := TExternalClassWrapper.Create;
  end;
  
  exports
    GetExternalClassWrapper;
  
  begin
  
  end.

• die originale Unit (liegt nur als DCU vor)
  
  Delphi-Quellcode:

  unit ExternalClass;
  
  // originale Unit, die nicht geändert werden kann,
  // da diese nur als DCU vorliegt
  
  interface
  
  uses
    Classes;
  
  type
    TExternalClass = class
    public
      procedure DoSomething( AStream : TStream );
    end;
  
  implementation
  
  { TExternalClass }
  
  procedure TExternalClass.DoSomething( AStream : TStream );
  var
    LWriter : TStreamWriter;
  begin
    LWriter := TStreamWriter.Create( AStream );
    try
      LWriter.Write( 'Written by ExternalClass' );
    finally
      LWriter.Free;
    end;
  end;
  
  end.

• Der Wrapper für die Klasse und das Interface
  
  Delphi-Quellcode:

  unit ExternalClassLibWrapper;
  
  interface
  
  uses
    ActiveX, Classes, Vcl.AxCtrls,
    ExternalClassIntf, ExternalClass;
  
  type
    TExternalClassWrapper = class( TInterfacedObject, IExternalClassWrapper )
    private
      FInstance : TExternalClass;
    public
      constructor Create;
      destructor Destroy; override;
  
      procedure DoSomething( AStream : IStream ); safecall;
    end;
  
  implementation
  
  { TExternalClassWrapper }
  
  constructor TExternalClassWrapper.Create;
  begin
    inherited Create;
    FInstance := TExternalClass.Create;
  end;
  
  destructor TExternalClassWrapper.Destroy;
  begin
    FInstance.Free;
    inherited;
  end;
  
  procedure TExternalClassWrapper.DoSomething( AStream : IStream );
  var
    LStream : TStream;
  begin
    LStream := TOleStream.Create( AStream );
    try
      FInstance.DoSomething( LStream );
    finally
      LStream.Free;
    end;
  end;
  
  end.

• Das Interface (das teilen sich sowohl DLL als auch die Anwendung)
  
  Delphi-Quellcode:

  unit ExternalClassIntf;
  
  interface
  
  uses
    ActiveX;
  
  type
    IExternalClassWrapper = interface
      ['{9AC01751-00EB-49D8-9FBA-3BDB1EA5F2D9}']
      procedure DoSomething( AStream : IStream ); safecall;
    end;
  
  implementation
  
  end.

• Testprogramm
  
  Delphi-Quellcode:

  program dp_180689_app;
  
  {$APPTYPE CONSOLE}
  {$R *.res}
  
  uses
    System.SysUtils,
    System.Classes,
    ExternalClassIntf in 'ExternalClassIntf.pas',
    ExternalClass in 'ExternalClass.pas';
  
  procedure Main;
  var
    LStream : TStream;
    LExternal : TExternalClass;
    LReader : TStreamReader;
  begin
    LStream := TMemoryStream.Create;
    try
  
      LExternal := TExternalClass.Create;
      try
        LExternal.DoSomething( LStream );
      finally
        LExternal.Free;
      end;
  
      LStream.Seek( 0, soFromBeginning );
  
      LReader := TStreamReader.Create( LStream );
      try
        Writeln( LReader.ReadToEnd );
      finally
        LReader.Free;
      end;
  
    finally
      LStream.Free;
    end;
  end;
  
  begin
    ReportMemoryLeaksOnShutdown := True;
    try
      Main;
    except
      on E : Exception do
        Writeln( E.ClassName, ': ', E.Message );
    end;
    ReadLn;
  end.

• Wrapper (Unit und Klasse folgen der selben Namenskonvention, dadurch spart man sich Tipparbeit)
  
  Delphi-Quellcode:

  unit ExternalClass;
  
  interface
  
  uses
    Classes,
    ExternalClassIntf;
  
  type
    TExternalClass = class
    private
      FInstance : IExternalClassWrapper;
    public
      constructor Create;
      procedure DoSomething( AStream : TStream );
    end;
  
  implementation
  
  uses
    ActiveX;
  
  function GetExternalClassWrapper : IExternalClassWrapper; safecall; external 'dp_180689_lib.dll' delayed;
  
  { TExternalClass }
  
  constructor TExternalClass.Create;
  begin
    inherited Create;
    FInstance := GetExternalClassWrapper;
  end;
  
  procedure TExternalClass.DoSomething( AStream : TStream );
  begin
    FInstance.DoSomething( TStreamAdapter.Create( AStream, soReference ) );
  end;
  
  end.