Delphi – Setting the OnClick procedure of a Delphi button at runtime


I have a program in which I need to update a database table with information entered into edit boxes, with a button at the end to do the updating. However, the form is created at runtime and all the elements including the button are also created in the same way. I figured a way to allow the database arguments would be to define a procedure to update the database such as:

procedure UpdateDatabase(Field1,Field2,Field3:string);
//update database here...

Then assign the OnClick event of my button to this procedure with the parameters pre filled like:

Button1.OnClick := UpdateDatabase(Edit1.text,Edit2.Text,Edit3.Text);

However the types are incompatible as it requires a different data type. I also noticed that parameters can't usually be passed into a OnClick function. Is there actually a way of achieving what I have proposed?

This is my current create button code:

function buttonCreate(onClickEvent: TProcedure; 
  left: integer; top: integer; width: integer; height: integer; 
  anchors: TAnchors; caption: string; parent: TWinControl; form: TForm;): TButton;
  theButton: TButton;
  theButton := TButton.Create(form);
  theButton.width := width;
  theButton.height := height;
  theButton.left := left; := top;
  theButton.parent := parent;
  theButton.anchors := anchors;
  //theButton.OnClick := onClickEvent;
  theButton.Caption := caption;
  result := theButton;

Any and all help appreciated!

Best Solution

Event handlers must be declared exactly how the event type is defined. An OnClick event is declared as a TNotifyEvent which takes parameters (Sender: TObject). You cannot break that rule.

In your case, you can wrap your own procedure inside of the event handler, like so...

procedure TForm1.Button1Click(Sender: TObject);

Note that TNotifyEvent is a procedure "of object", which means your event handler must be declared inside of an object. In your case, the event handler should be declared inside your form (not in a global location).

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