如何将 integer 的集合转换为 Delphi 中的逗号分隔字符串？

Question

  private const
    CA_2_4_RECOMMENDED_CHANNELS = [1, 5, 6, 9, 11, 13];

I can use the "for" loop, but how can I use some generics to get a comma separated string like '1, 5, 6, 9, 11, 13' without any loops?

Answer 1

The simplest way uses the TStringList class from the System.Classes unit:

const
  CA_2_4_RECOMMENDED_CHANNELS = [1, 5, 6, 9, 11, 13];
var
  c: integer;
  sl: TStringList;
begin
  sl := TStringList.Create;
  try
    for c in CA_2_4_RECOMMENDED_CHANNELS do
      sl.Add(c.ToString);
    writeln(sl.CommaText);
  finally
    sl.Free;
  end;
end;

But even with this solution, a For-Each loop is required to fill the StringList. A solution where each element must not be touched does not exist from my point of view.

Answer 2

You can do this with RTTI, for example.

program Project1;

{$APPTYPE CONSOLE}

{$R *.res}

uses
  System.SysUtils, System.Rtti;




type
  TMySet=set of byte;
var
  m: TMySet;
  v: TValue;
begin
  try
    m := [1, 5, 6, 9, 11, 13];
    v := TValue.From<TMySet>(m);
    writeln(v.ToString());
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.