Delphi 新语法：For in语句

据说Delphi 2005开始支持For in语句.并没有深入调查,依然从万一博客学习并整理.

一、遍历 TStrings

var
  List: TStrings;
  s: string;
begin
  List := TStringList.Create;
  List.CommaText := 'aaa,bbb,ccc';

  for s in List do
    ShowMessage(s);

  List.Free;
end;

二、遍历数组

var
  Arr: array[0..2] of Byte;
  i: Integer;
  b: Byte;
begin
  for i := Low(Arr) to High(Arr) do
    Arr[i] := Random(MAXBYTE);

  for b in Arr do
    ShowMessage(IntToStr(b));
end;

三、遍历子界

{例1}
var
  sub: 0..9;
  str: string;
begin
  str := '';
  for sub in [Low(sub)..High(sub)] do
    str := str + IntToStr(sub); 

  ShowMessage(str); {0123456789}
end;

{例2}
type
  TSub = 'A'..'G';
var
  sub: TSub;
  str: string;
begin
  str := '';
  for sub in [Low(sub)..High(sub)] do
    str := str + sub; 

  ShowMessage(str); {ABCDEFG}
end;

{例3}
var
  sub: Byte; {Byte 应该算是个 0..255 的子界}
  num: Cardinal;
begin
  num := 0;
  for sub in [Low(sub)..High(sub)] do
    Inc(num, sub); 

  ShowMessage(IntToStr(num)); {32640}
end;

四、遍历枚举

type
  TEnum = (Red,Green,Blue);
var
  enum: TEnum;
  count: Integer;
begin
  count := 0;
  for enum in [Low(enum)..High(enum)] do
    Inc(count);

  ShowMessage(IntToStr(count)); {3}
end;

五、遍历集合

type
  TEnum = (Red,Green,Blue,Yellow);
  TSet = set of TEnum;
var
  set1: set of TEnum;
  set2: TSet;
  elem: Tenum;
  count: Integer;
begin
  set1 := [Red, Yellow];
  count := 0;
  for elem in set1 do Inc(count);
  ShowMessage(IntToStr(count)); {2}

  set2 := [Red..Yellow];
  count := 0;
  for elem in set2 do Inc(count);
  ShowMessage(IntToStr(count)); {4}
end;

六、遍历字符串

var
  str: string;
  c: Char;
begin
  str := 'ABCD';
  for c in str do
    ShowMessage(c);
end;