Adding a new property for component

[Elmug]

Good people,

So far I have managed to use some basic components, with their properties as designed.

However, I have been wondering how difficult  (or simple) it would be to add to one or various components a new property. In its simplest way, perhaps to hold the value of a Real. Akin to the property Tag which can hold an integer.

I suppose it involves first creating a new type TagReal (or so), and when that new object type is declared, ...then what?

I am basically asking for a simple description of what I involves, in a few sentences, and hopefully some correct terminology by which I can search the web without going astray.

Or, some links to study the subject would also be appreciated.

And I don't mean create a new component, but rather add a property to an existing one, or copy an existing one to modify it with an extra property.

I do have the hunch that this may not be one thing to do. However, I have been very happy to be corrected in this forum.

[Blaazen]

Adding new property to existing component is easy. Example:

Code: [Select]

TMyLabel = class(TLabel)
  private
    FMyReal: Double;
  protected
  public
  end;       
In this case, I put FMyReal as private but you can set it as public or protected as well.
You can create this component in code like this:

Code: [Select]

var MyLabel: TMyLabel;
..........
MyLabel:=TMyLabel.Create(self);
  with MyLabel do
    begin
      Caption:='MyLabel';
      Left:=25;
      FMyReal:=3.14;
      Parent:=self;
    end;
Adding component to component palette and work with it in Object Inspector is somewhat more complicated, read wiki: http://wiki.lazarus.freepascal.org/How_To_Write_Lazarus_Component

[typo]

Code: [Select]

TMyLabel = class(TLabel)
  private
    FMyReal: Double;  // this is a Field, not a property
  protected
  public
    property MyReal :Double read FMyReal write FMyReal;
  end;     

Code: [Select]

var MyLabel: TMyLabel;
..........
MyLabel:=TMyLabel.Create(self);
  with MyLabel do
    begin
      Caption:='MyLabel';
      Left:=25;
      MyReal:=3.14;
      Parent:=self;
    end;

[Elmug]

Thank you so much, both much appreated.

What you explain, Blaazen, is kind of what I sensed would be much more of a challenge that I can not approach nor need to right now: adding things to the palette.

These knowledgeable simple solutions will avoid me from some code convolutions that teach a lot, but there are better ways often.

So, using what is described her is one thing I certainly will try out soon.

The code snippet you provide is very clear too, Typo. Thanks!