核心提示:Classes.TList Classes.TCollection Classes.TStrings Classes.TInterfaceList Classes.TComponent Menus.T...
Classes.TList Classes.TCollection
Classes.TStrings
Classes.TInterfaceList
Classes.TComponent
Menus.TMenuItem
ActnList.TCustomActionList
DB.TFields
ComCtrls.TListItems
ComCtrls.TTreeNodes
ComCtrls.TToolBar
首先来看一个简单的例子:
procedure ShowListStr(StrList: TStrings);
var
tmpStr: String;
begin
for tmpStr in StrList do
ShowMessage(tmpStr); //这样就可以历遍整个SrList的值了,比以前用for i to do 快了很多吧
end;
再看看这个:(数组历遍)
type
TIntArray = array[0..9] of Integer;
TGenericIntArray = array of Integer;
var
IntArray1: array[0..9] of Integer = (1, 2, 3, 4, 5, 6, 7, 8, 9, 10);
IntArray2: array[1..2] of TIntArray = ((11, 12, 13, 14, 15, 16, 17, 18, 19, 20),
(21, 22, 23, 24, 25, 26, 27, 28, 29, 30));
IntArrayTemp: TIntArray;
IGenericIntArray: TGenericIntArray;
i: integer;
begin
for i in IntArray1 do
begin
ShowMessage(IntToStr(i)); //这样便可以历遍这个数组,不用再用for High Low等等函数了
end;
for i in IntArray2 do //多维数组的历遍
for i in IGenericIntArray do
begin
ShowMessage(IntToStr(i));
end;
end;
看了后是不是觉得历遍一个数组比以前方便多了.
再看看For in 在字符串中的应用:
var
C: Char;
Str1,Str2: String;
begin
Str1 := 'Hello Everybody,I am Kevin...';
Str2 := '';
for C in S1 do //这样就已经历遍了一个字符串,并进行了拆解...
Str2 := Str2 + C;
if Str1 = Str2 then
ShowMessage('Success!');
end;
再看看如何历遍集合型的数据类型的:
type
TMyThing = (one, two, three);
TMySet = set of TMyThing;
TCharSet = set of Char;
var
MySet: TMySet;
MyThing: TMyThing;
CharSet: TCharSet;
C: Char;
begin
MySet := [one, two, three];
for MyThing in MySet do //历遍集合
begin
// 做相关的处理
end;
CharSet := [#0..#255];
for C in CharSet do
begin
// 做相关的处理
end;
end.
下面这个更加有用,历遍类
这个类必须实现一个公用的方法为:GetEnumerator(),此方法返回的是一个类.而另一个类必须实现一个公用的方法为:MoveNext()和一个名为Current的属性.方法返回类型为Boolean;看例子:
type
TMyIntArray = array of Integer;
TMyEnumerator = class
Values: TMyIntArray;
Index: Integer;
public
constructor Create;
function GetCurrent: Integer;
function MoveNext: Boolean; //这个为实现的MoveNext方法
property Current: Integer read GetCurrent;
end;
TMyContainer = class
public
function GetEnumerator: TMyEnumerator; //这个为实现的GetEnumerator的方法.
end;
constructor TMyEnumerator.Create;
begin
inherited Create;
Values := TMyIntArray.Create(100, 200, 300);
Index := -1;
end;
function TMyEnumerator.MoveNext: Boolean;
begin
if Index < High(Values) then
begin
Inc(Index);
Result := True;
end
else
Result := False;
end;
function TMyEnumerator.GetCurrent: Integer;
begin
Result := Values[Index];
end;
function TMyContainer.GetEnumerator: TMyEnumerator;
begin
Result := TMyEnumerator.Create;
end;
var
MyContainer: TMyContainer;
I: Integer;
Counter: Integer;
begin
MyContainer := TMyContainer.Create;
for I in MyContainer do //历遍,并把TMyEnumerator的Current进行累加...
Inc(Counter, I);
ShowMessage(IntToStr(Counter)); //值为600
end.
从上面可以看到通过Current就可以实现很大功能了,我们只需把Current的类型变一个,就可以做到很方便的功能.
总结,从For In语法看到,可以给我们编码时带来很多方便