Delphi的in循环

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今天无意中看到了一篇文章里面提起到了for in do 循环，之前没有用过的方法。

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;

如果你用过C#的话你可能会觉得眼熟，和C#的foreach循环类似。
原作者万一的博客，原址：
http://www.cnblogs.com/del/archive/2008/11/12/1332011.html

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