枚举

枚举：它用于声明一组命名的常数，当一个变量有几种可能的取值时，可以将它定义为枚举类型。

//定义
type
  Colors = (Red, Yellow, Green, Cyan, Blue, Violet);
  Suit = (Club, Diamond, Heart, Spade);



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//举例：
type
  Colors = (Red, Yellow, Green, Cyan, Blue, Violet);
var
  C: Colors;
begin
  C := Red;
  ShowMessage(IntToStr(Ord(C)));  //0
  C := Blue;
  ShowMessage(IntToStr(Ord(C)));  //4

  C := Green;
  ShowMessage(IntToStr(Integer(C)));  //2; 获取元素位置用 Integer 也可以
end;



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//举例2：
type
  Tabc = (a=5,b=10,c=a+b);
var
  ta,tb,tc: Tabc;
begin
  ta := a;
  tb := b;
  tc := c;
  ShowMessage(IntToStr(Ord(ta)));  //5
  ShowMessage(IntToStr(Ord(tb)));  //10
  ShowMessage(IntToStr(Ord(tc)));  //15
end;



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//获取枚举元素总数：
type
  TMyEnum = (Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday);
var
  m: TMyEnum;
  num: Integer;
begin
  num := 0;
  for m := Low(TMyEnum) to High(TMyEnum) do
    Inc(num);

  ShowMessage(IntToStr(num));  // 7
end;



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//返回枚举元素的字符串标识：
uses TypInfo;  //需要uses的单元
type
  TMyEnum = (Monday,Tuesday,Wednesday,Thursday,Friday,Saturday,Sunday);

procedure TForm1.Button1Click(Sender: TObject);
var
  str: string;
begin
  str := TypInfo.GetEnumName(TypeInfo(TMyEnum),1);
  ShowMessage(str);  //Tuesday
end;



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//获取对象枚举值的字符串表式：
uses TypInfo;  //需要uses的单元

procedure TForm1.FormCreate(Sender: TObject);
var
  str: string;
begin
  str := GetEnumProp(Self, 'BorderStyle');
  ShowMessage(str); { bsSizeable }
end;