DELPHI: Declare HTTPRIO.OnBeforeExecute in TComponent

Question

Using Delphi 2005, I have created a test app (using a TForm) to test a SOAP API. Unfortunately this API has declared some enums (Application, System and Terminal) which are reserved by Delphi. I renamed the enums in the SOAP file (_Application, _Terminal and _System) and was able to write OnBeforeExecute and OnAfterExecute methods to replace these renamed enums with the original names before and after submitting.

I am now trying to incorporate this into my larger project and would like to capture all the code for this SOAP API in a class file (no form). With my tester app I added a THTTPRIO object to the form (from the Tool Palette) and could easily set the OnBeforeExecute and OnAfterExecute methods in the Object Inspector. Now using the class (a TComponent) I cannot add the THTTPRIO object using Tool Palette like I did with the form. I tried to create the THTTPRIO object via code but am getting some errors.

I get the error E2009 incompatible types: 'Parameter lists differ' on FEPS_HTTPRIO.OnAfterExecute := HTTPRIOAfterExecute; (see code below)

Why do I get the error on this but not on FEPS_HTTPRIO.OnBeforeExecute := HTTPRIOBeforeExecute; and how can I implement these two methods within my class?

Here is how I created the THTTPRIO via code:

unit c_MoSh;

interface

uses classes, forms, Windows, SysUtils, c_MoShAPI, InvokeRegistry, controls;

Type

  TMoSh = class(TComponent)
  private
    ...
    procedure HTTPRIOBeforeExecute(const MethodName: string;
                                    var SOAPRequest: WideString);
    procedure HTTPRIOAfterExecute(const MethodName: string;
                                    var SOAPResponse: TStream);

  ...

constructor TMoSh.Create();
begin
  FEPS_HTTPRIO := THTTPRIO.Create(self);
  FEPS_HTTPRIO.OnBeforeExecute := HTTPRIOBeforeExecute;
  FEPS_HTTPRIO.OnAfterExecute := HTTPRIOAfterExecute;       <-- Error line

end;

procedure TMosquitoShield.HTTPRIOBeforeExecute(const MethodName: string;
                                    var SOAPRequest: WideString);
var
  tmpString: TStringList;
begin

  try

    SOAPRequest := StringReplace(SOAPRequest,'<ReversalType>_Application','<ReversalType>Application',[RfReplaceAll]);
    SOAPRequest := StringReplace(SOAPRequest,'<ReversalType>_System','<ReversalType>System',[RfReplaceAll]);
    SOAPRequest := StringReplace(SOAPRequest,'<CardholderPresentCode>NotPresent2','<CardholderPresentCode>NotPresent',[RfReplaceAll]);
    SOAPRequest := StringReplace(SOAPRequest,'<DeviceInputCode>NotUsed3','<DeviceInputCode>NotUsed',[RfReplaceAll]);

  except
    on ER : ERemotableException do
      ShowMessage(ER.ClassName + ' error raised, with message : ' + ER.FaultDetail + ' :: '
                    + ER.Message);

    on E : Exception do
      ShowMessage(E.ClassName + ' error raised, with message : ' + E.Message);
  end;

end;

procedure TMosquitoShield.HTTPRIOAfterExecute(const MethodName: string;
                                    var SOAPResponse: TStream);
var
  tmpString: TStringList;
begin

  try
    tmpString := TStringList.Create;
    SOAPResponse.Position := 0;
    tmpString.LoadFromStream(SOAPResponse);

    tmpString.Text := StringReplace(tmpString.Text,'Application','_Application',[RfReplaceAll]);
    tmpString.Text := StringReplace(tmpString.Text,'System','_System',[RfReplaceAll]);
    tmpString.Text := StringReplace(tmpString.Text,'<PASSUpdaterOption>Null','<PASSUpdaterOption>Null2',[RfReplaceAll]);
    tmpString.Text := StringReplace(tmpString.Text,'<TransactionSetupMethod>Null','<TransactionSetupMethod>Null3',[RfReplaceAll]);
    tmpString.Text := StringReplace(tmpString.Text,'<Device>Null','<Device>Null4',[RfReplaceAll]);
    tmpString.Text := StringReplace(tmpString.Text,'<ConsentCode>NotUsed','<ConsentCode>NotUsed2',[RfReplaceAll]);
    tmpString.Text := StringReplace(tmpString.Text,'<DeviceInputCode>NotUsed','<DeviceInputCode>NotUsed3',[RfReplaceAll]);

    SOAPResponse.Position := 0;
    tmpString.SaveToStream(SOAPResponse);

  except
    on ER : ERemotableException do
      ShowMessage(ER.ClassName + ' error raised, with message : ' + ER.FaultDetail + ' :: '
                    + ER.Message);

    on E : Exception do
      ShowMessage(E.ClassName + ' error raised, with message : ' + E.Message);
  end;

end;

Answer 1

Your method signature has to match the signature of the event type exactly. Remove var before SOAPResponse parameter in your HTTPRIOAfterExecute method.

As for the name conflicts you describe, you can avoid them by prefixing code elements (enumeration members, variables, types etc) with the unit name: SOAP_API.Application - for SOAP enumeration, and Forms.Application for Delphi Application global.