首先我们要知道哪些类型可以用For In吧,下面就是:
- for Element in ArrayExpr do Stmt; 数组
- for Element in StringExpr do Stmt; 字符串
- for Element in SetExpr do Stmt; 集合
- for Element in CollectionExpr do Stmt; 集合
- for Element in Record do Stmt; 结构体
我们来看例子:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | type
THuangJacky = (hjA,hjB,hjC,hjD);
TJackyHuang =record
a,b,c:Integer;
end;
const
stringExpr='HuangJacky';
arrayExpr:array[0..5]ofInteger= (1,2,3,4,5,6);
setExpr:setofTHuangJacky = [hjA,hjB,hjD];
procedureTForm1.FormCreate(Sender: TObject);
var
I:Integer;
C:Char;
D:THuangJacky;
F:TComponent;
begin
forcinstringExprdo
ShowMessage(C);
foriinarrayExprdo
ShowMessage(IntToStr(i));
fordinsetExprdo
ShowMessage(IntToStr(Ord(d)));
forFinSelfdo
ShowMessage(f.Name);
end;
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是不是很爽呀?哈哈,Delphi也与时俱进呀.
之前写了类助手文章中,老赵问是不是扩展方法,因为对C#没有了解到这么多,所以不知道.
那么我们在Java中要For In必须实现Iterator吧.
那么Delphi的会不会也要呢?
是的,如果我们要自己的类支持For In的话,就必须满足下面的条件:
1 必须有个公共方法GetEnumerator(),这个方法返回值是一个类,接口或者记录体.
2 上面返回的类,接口或者记录体中又必须有公共方法MoveNext(),这个方法的返回值是Boolean.
3 1中返回的类,接口或者记录体中必须有一个只读的属性Current,类型要和集合中的元素一样.
说了这么多,看个例子:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 | type
TMyIntArray =arrayofInteger;
TMyEnumerator =class
Values: TMyIntArray;
Index:Integer;
public
constructorCreate;
functionGetCurrent:Integer;
functionMoveNext:Boolean;
propertyCurrent:Integerread GetCurrent;
end;
TMyContainer =class
public
functionGetEnumerator: TMyEnumerator;
end;
constructorTMyEnumerator.Create;
begin
inheritedCreate;
Values := TMyIntArray.Create(100,200,300);
Index := -1;
end;
functionTMyEnumerator.MoveNext:Boolean;
begin
ifIndex < High(Values)then
begin
Inc(Index);
Result :=True;
end
else
Result :=False;
end;
functionTMyEnumerator.GetCurrent:Integer;
begin
Result := Values[Index];
end;
functionTMyContainer.GetEnumerator: TMyEnumerator;
begin
Result := TMyEnumerator.Create;
end;
var
MyContainer: TMyContainer;
I:Integer;
Counter:Integer;
begin
MyContainer := TMyContainer.Create;
Counter :=0;
forIinMyContainerdo
Inc(Counter, I);
WriteLn('Counter = ', Counter);
end.
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https://blog.csdn.net/rocklee/article/details/48627165