Why use property in a class?

Question

I was just wondering about why should I use property in a class instead of \"normal\" variables (class attributes?). What I mean is this:

TSampleClass = clas         


        

Answer 1

One of main reason of using properties (regardless of it's more OO) is the validation of the input, for example if you need to limit the age of an employee class to be in valid range like 18..40

  TEmp = class
  private
    FName: string;
    FAge: Integer;
    procedure SetAge(const Value: Integer);
    procedure SetName(const Value: string);
  published
    property Name:string read FName write SetName;
    property Age:Integer read FAge write SetAge;
  end;

.....

procedure TEmp.SetAge(const Value: Integer);
begin
  if not (Value in [18..40]) then
    raise Exception.Create('Age must be between 18 and 40')
  else
    FAge := Value;
end;