动态数组怎样用啊

我定义了这样一个变量
type
  SquareType=Record
    Ary:byte;
    color:byte;
  end;type
  TGameData=packed record
    SaveAry:array of array of SquareType;
    flag:byte;
    NowStyle:byte;
    GoButtom:integer;
    GoLeft:integer;
    CanStop,NotLeft,NotRight,NotChange:integer;
  end;var
  Rec:TGameData;
然后我用
  setlength(rec.SaveAry,20,20);
设置它,再用循环给它赋值后,就是读不出它的值,改为静态就没事了