1.Class FIElds
//例1成員變量
type
TAncestor=class
Value:Integer;
end;
TDescendant=class(TAncestor)
Value:string; //hidestheinheritedValuefIEld
end;
var
MyObject:TAncestor;
begin
MyObject:=TDescendant.Create;
MyObject.Value:='Hello!' //error
(MyObjectasTDescendant).Value:='Hello!' //works!
end;
//例2靜態字段
type
TMyClass=class
public
classvar //IntroduceablockofclassstaticfIElds.
Red:Integer;
Green:Integer;
Blue:Integer;
var //Endstheclassvarblock.
InstanceFIEld:Integer;
end;
//靜態字段可以單獨調用
TMyClass.Red:=1;
TMyClass.Green:=2;
TMyClass.Blue:=3;
//靜態字段也可以通過對象實例調用
var
myObject:TMyClass;
myObject.Red:=1;
myObject.Green:=2;
myObject.Blue:=3;
2.Method Binding
//StaticMethods
//例1
type
TFigure=class
procedureDraw;
end;
TRectangle=class(TFigure)
procedureDraw;
end;
var
Figure:TFigure;
Rectangle:TRectangle;
begin
Figure:=TFigure.Create;
Figure.Draw; //callsTFigure.Draw
Figure.Destroy;
Figure:=TRectangle.Create;
Figure.Draw; //callsTFigure.Draw
TRectangle(Figure).Draw; //callsTRectangle.Draw
Figure.Destroy;
Rectangle:=TRectangle.Create;
Rectangle.Draw; //callsTRectangle.Draw
Rectangle.Destroy;
end;
//虛方法和動態方法
type
TFigure=class
procedureDraw;virtual;
end;
TRectangle=class(TFigure)
procedureDraw;override;
end;
TEllipse=class(TFigure)
procedureDraw;override;
end;
var
Figure:TFigure;
begin
Figure:=TRectangle.Create;
Figure.Draw; //callsTRectangle.Draw
Figure.Destroy;
Figure:=TEllipse.Create;
Figure.Draw; //callsTEllipse.Draw
Figure.Destroy;
end;
//例2
type
T1=class(TObject)
procedureAct;virtual;
end;
T2=class(T1)
procedureAct; //Actisredeclared,butnotoverridden
end;
var
SomeObject:T1;
begin
SomeObject:=T2.Create;
SomeObject.Act; //callsT1.Act
end;
//類方法ClassMethod
//OrdinaryClassMethods
//ThedefinitionofaclassmethodmustbeginwiththereservedWordclass.Forexample,
type
TFigure=class
public
classfunctionSupports(Operation:string):Boolean;virtual;
classprocedureGetInfo(varInfo:TFigureInfo);virtual;
……
end;
//Thedefiningdeclarationofaclassmethodmustalsobeginwithclass.Forexample,
classprocedureTFigure.GetInfo(varInfo:TFigureInfo);
begin
……
end;
//ClassStaticMethods
type
TMyClass=class
strictprivate
classvar
FX:Integer;
strictprotected
//Note:AccessorsforclasspropertIEsmustbedeclaredclassstatic.
classfunctionGetX:Integer;static;
classprocedureSetX(val:Integer);static;
public
classpropertyX:IntegerreadGetXwriteSetX;
classprocedureStatProc(s:String);static;
end;
//調用
TMyClass.X:=17;
TMyClass.StatProc('Hello');
3.函數重載
type
T1=class(TObject)
procedureTest(I:Integer);overload;virtual;
end;
T2=class(T1)
procedureTest(S:string);reintroduce;overload;
end;
……
SomeObject:=T2.Create;
SomeObject.Test('Hello!'); //callsT2.Test
SomeObject.Test(7); //callsT1.Test
4構造函數
type
TShape=class(TGraphicControl)
private
FPen:TPen;
FBrush:TBrush;
procedurePenChanged(Sender:TObject);
procedureBrushChanged(Sender:TObject);
public
constructorCreate(Owner:TComponent);override;
destructorDestroy;override;
……
end;
constructorTShape.Create(Owner:TComponent);
begin
inheritedCreate(Owner); //Initializeinheritedparts
Width:=65; //ChangeinheritedpropertIEs
Height:=65;
FPen:=TPen.Create; //InitializenewfIElds
FPen.OnChange:=PenChanged;
FBrush:=TBrush.Create;
FBrush.OnChange:=BrushChanged;
end;
