Class Helper for Delphi's TStrings: Implemented Add(Variant)

Implementing ListBox1.Add(5) and ListBox1.Add(True)

_{Tip submitted by Jens Borrisholt}

In Delphi, the TStrings is the base class for objects that represent a list of strings. Examples include Lines property of a TMemo, Items property of a TListBox or TComboBox, etc.

To add strings to the list you use the Add method which accepts a string parameter.

When you need to add integer values, boolean values or any other non-string values to the list you need to use some of the RTL's conversion routines (from int to string for example).

Wouldn't it be better if you can simply say "Add(2008)" or "Add(True)"?

Class Helper for TStrings - Add method to accept Variant types

Here's the implementation of the TStringsHelper unit to extend the TStrings class's Add method:

unit TStringsHelperU;



//class helper for TStrings

//delphi.about.com



interface



uses Classes;



type

  TStringsHelper = class helper for TStrings

  public

    function Add(const V: Variant): Integer; overload;

    function Add(const Args: array of Variant): Integer; overload;

  end;



implementation



uses Variants;



function TStringsHelper.Add(const Args: array of variant): Integer;

var

  tmp: string;

  cnt: Integer;

begin

  tmp := '';

  for cnt := Low(Args) to High(Args) do

    tmp := tmp + VarToStr(Args[cnt]) ;

  result := Add(tmp) ;

end;



function TStringsHelper.Add(const V: Variant): Integer;

begin

  Result := Add([V]) ;

end;



end.

An example of usage:

with ListBox1.Items do

begin

  Add('delphi.about.com') ;

  Add(2008) ;

  Add(true) ;

  Add(['Only ', 1, true, ' line']) ;

end;

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