Incorrect parameter for custom event handler

c++ builder

    Sponsored Links


  • 1. Disable DBEdit ---Colour
    When I disable DBEdit,, the colour of the word is grey. Can I change it to other colours?
  • 2. Error: Control has no parent window
    Hi All, Another strange question. I completely converted the TEdit source from delphi to c++builder.Please see the attachment. However, when I place the control onto the form in Designer, it throws a exception with msg, 'Control MyEdit has no parent window'. I have carefully checked the code by myself with the pascal source, I donot think I made any wrong. If I un-comment the first line of the MyEdit constructor, it seems ok that can be placed on the form with Win31 look and feel(yes, Win31, no border). But when at runtime, the control is run in a another seperated window. strange... I have searched on the net and found some clues for this problem. it seems that it's a bug related to C++Builder. I am using C++Builder6 with SP4 patched. the version is Version 6.0(Build 10.166). my OS is Win2k with SP4. Thanks In Advanced! chenzero
  • 3. Passing in OnMouseDown and OnMouseUp event handlers to an object's constructor
    Hi all, I have created a class which contains many TShapes, TLabels and TPanels. What I want to be able to do is when creating this class, is passing in a pointer to OnMouseDown and OnMouseUp events. Thereby, the user of the class can create their own event handlers for those events. The idea is that by passing in the event handlers, these event handlers are assigned to the appropriate events for each of the objects in the class. However, I am having trouble declaring the constructor: eg. class SpecialButton : public TObject { __published: TShape *TLCorner; TShape *TRCorner; // ...etc.... __public: __fastcall SpecialButton(TMouseEvent mouseDown, TMouseEvent mouseUp); // ?????? }; Your suggestions on this would be greatly appreciated. Thanks, Kyzer
  • 4. Link Error
    Hi, > eg, I wrote a component, MyBevel, which uses some extra function defined in > another cpp/h file. The component package successfully installed. However, > when I built the application, the compiler said > > '[Linker Error] Unresolved external '__fastcall a_cc()' referenced from > D:\BORLAND\CBUILDER6\PROJECTS\LIB\TESTVCL.LIB|E:\MyBevel.cpp' > I think you need a #pragma link of either an .obj or .lib. This places a comment record in your OBJ, that when encoutered by the linker, will be the same as having that .obj or .lib on the linker command line. Of course, you also have to distribute the .obj or .lib with your package. --Craig
  • 5. csFix-ups Sample
    would anybody give me some sample of using ComponentState.Contain(csFix-ups )? thank you

Incorrect parameter for custom event handler

Postby Myles Rippenhagen » Wed, 26 Oct 2005 02:43:50 GMT


I have created several custom components and generally have had great 
success with them, but I am currently running into a problem where when I 
double-click on a published custom event (on the "Events" tab of the "Object 
Inspector" in the IDE), the inserted method declaration contains the wrong 
variable name.  The signature matches another, similar custom event, and it 
seems to be picking up the parameter name from this other definition.  I 
have double-checked that I am referencing the correct typedef in the 
definition of my custom component and I didn't see any problem.  I am using 
BCB6 Enterprise on WinXP.  Following are the important bits of the code.

typedef void __fastcall (__closure *BeforePostEvent) (TObject* Sender, bool 
typedef void __fastcall (__closure *OnPutToDatabaseEvent) (TObject* Sender, 
bool &DoDefault);
   OnPutToDatabaseEvent FOnPutToDatabaseEvent;
   __property OnPutToDatabaseEvent OnPutToDatabase = 
{read=FOnPutToDatabaseEvent, write=FOnPutToDatabaseEvent};

When I double-click on the "OnPutToDatabase" event in the IDE, the inserted 
code labels the bool parameter "CanPost" instead of "DoDefault".  It appears 
to just pick up the first typedef with a matching signature instead of using 
the typdef that I specified.

Any suggestions??

Re: Incorrect parameter for custom event handler

Postby Remy Lebeau (TeamB) » Wed, 26 Oct 2005 03:12:24 GMT

That is a long-standing known issue.  The OI matches events by signatures
only, not names.  You have two different events that have the exact same
signature (return value, calling convention, parameter data types, and
parameter ordering).  The OI always generates code using the first event
type that matches the required signature.

That is exactly why you are seeing what you have described.  There is
nothing you can do to prevent the OI from behaving that way.  You will just
have to change the signature of one of your events so that they no longer
match each other.

The OI does not care about typedefs.  It only cares about signatures.


Similar Threads:

1.Why event handler first parameters are incorrect

I noticed that DataGridView CellValidated() and other event handler first 
parameter is object:


        void Grid_CellValidated(object sender, DataGridViewCellEventArgs e) 

Why ? Correct signature must be

void Grid_CellValidated(DataGridView sender, DataGridViewCellEventArgs e) {


2.Custom event handler

Hello, all.  I am trying to develop my first component and I am trying to
figure something out.  I created a MouseMove event handler for my component
(TMyComponent::MouseMove) and it works fine.  I added my component to a new
project (TMyComponent *MyComponent1) and I want perform a task in the
MyComponent1MouseMove event.  My problem is that the TMyComponent::MouseMove
function is executing, but the TForm1::MyComponent1MouseMove function is
not.  I set the OnMouseMove event to MouseMove for the MyComponent1
instance, but it still only calls the component handler, not the custom
handler.  Why won't it call my custom handler?  Actually, I will need both
functions to execute.  Will I need to explicitly call
TMyComponent::MouseMove() from within the TForm1::MyComponent1MouseMove
function to get both to execute?  Any feedback will be greatly appreciated.



3.Custom event handlers in .NET Winforms

4.Custom Event Handler

I am getting an error down below, this same code works in VB, what gives?

private void Form1_Load(object sender, System.EventArgs e)


System.Windows.Forms.LinkLabel l = new System.Windows.Forms.LinkLabel();

FileSystemWatcher watcher = new FileSystemWatcher();

watcher.Path = @"C:\TempFolder";

watcher.Filter = "*.txt";

//error here: Cannot implicitly convert type System.EventHandler to

watcher.Created += new System.EventHandler(OnCreated);

watcher.EnableRaisingEvents = true;


private void OnCreated(object sender, System.EventArgs e)




5.Custom event handlers and searching a listview

6. Passing in a OnMouseDown/OnMouseUp event handler as a parameter of a function

7. How to pass more than two parameters in the event handler

8. TADODataset.Parameters.Refresh results in incorrect parameter names

Return to c++ builder


Who is online

Users browsing this forum: No registered users and 11 guest