Delphi XE中类成员的访问权限******

Delphi XE中类成员的访问权限 转老帅博客

共提供了6个关键词来用于限定访问权限：

public、private、protected、published、automated strict private 、 strict protected
其各自的含义为：

1. strict private：

   此区定义的字段或方法只能用于当前的类中。即T1中此区定义的成员只能在T1中使用。
2. strict protected：

此区定义的成员除能用于当前类中，还可用于当前类的任何子类中。 以上两种成员，同一个类的不同对象间也不能互访问。
3. private：

所限定的成员只能用于定义这个类的.pas文件或.dpr文件。
4. protected：

相当于将private扩展到任意子类均可见。
5. public：

对任何位置、任何类均可见。当某些成员未显式指定其访问权限时，Delphi默认为此public。
6. published：

访问权限与public相同。
7. automated：

用于Win32下的COM编程。

 

注意：strict private与strict protected从Delphi2007开始引入，之前的版本不存在这两种等级

在 published published published 区声明属性时应注意以下两点：

1. published published 属性的值只能是：有序类型、字符串接口变体方法指针以及上下界在 0到 31 之间的集合类型。实数不能是 Real48 类型。
2. 不能以同一个名字公布两个或更多的重载方法。

Delphi7之后Delphi的一些新特性

Abstract: See many of the major new language features in Delphi released after the Delphi 7 version

Language and Compiler Features Since Delphi 7
Inlining	Routines can now be marked with the inline directive.  This tells the compiler that, instead of actually calling the routine, it should emit code that includes the routine at the call site.
Operator Overloading	Delphi allows certain functions, or operators, to be overloaded within record declarations TMyClass = class class operator Add(a, b: TMyClass): TMyClass; // Addition of two operands of type TMyClass class operator Subtract(a, b: TMyClass): TMyclass; // Subtraction of type TMyClass class operator Implicit(a: Integer): TMyClass; // Implicit conversion of an Integer to type TMyClass class operator Implicit(a: TMyClass): Integer; // Implicit conversion of TMyClass to Integer class operator Explicit(a: Double): TMyClass; // Explicit conversion of a Double to TMyClass end; // Example implementation of Add class operator TMyClass.Add(a, b: TMyClass): TMyClass; begin ... end; var x, y: TMyClassbegin x := 12; // Implicit conversion from an Integer y := x + x; // Calls TMyClass.Add(a, b: TMyClass): TMyClass b := b + 100; // Calls TMyClass.Add(b, TMyClass.Implicit(100)) end;
Class Helpers	A class helper is a type that - when associated with another class - introduces additional method names and properties which may be used in the context of the associated class (or its descendants). Class helpers are a way to extend a class without using inheritance. A class helper simply introduces a wider scope for the compiler to use when resolving identifiers. When you declare a class helper, you state the helper name, and the name of the class you are going to extend with the helper. You can use the class helper any place where you can legally use the extended class. The compiler's resolution scope then becomes the original class, plus the class helper. Class helpers provide a way to extend a class, but they should not be viewed as a design tool to be used when developing new code. They should be used solely for their intended purpose, which is language and platform RTL binding. type TMyClass = class procedure MyProc; function MyFunc: Integer; end; ... procedure TMyClass.MyProc; var X: Integer; begin X := MyFunc; end; function TMyClass.MyFunc: Integer; begin ... end; ... type TMyClassHelper = class helper for TMyClass procedure HelloWorld; function MyFunc: Integer; end; ... procedure TMyClassHelper.HelloWorld; begin WriteLn(Self.ClassName); // Self refers to TMyClass type, not TMyClassHelper end; function TMyClassHelper.MyFunc: Integer; begin ... end; ... var X: TMyClass; begin X := TMyClass.Create; X.MyProc; // Calls TMyClass.MyProc X.HelloWorld; // Calls TMyClassHelper.HelloWorld X.MyFunc; // Calls TMyClassHelper.MyFunc end;
strict private	The private keyword actually creates a " friendship" relationship between classes in the same unit.  The strict private declaration creates a true private field, not viewable by any other class, not even classes in the same unit.
strict protected	Similar to the strict private declaration, strict protectedcreates a true protected member, visible only to the declaring class and its descendents.
Records with Methods	In addition to fields, records now may have properties and methods (including constructors), class properties, class methods, class fields, and nested types.  type TMyRecord = record type TInnerColorType = Integer; var Red: Integer; class var Blue: Integer; procedure printRed(); constructor Create(val: Integer); property RedProperty: TInnerColorType read Red write Red; class property BlueProp: TInnerColorType read Blue write Blue; end; constructor TMyRecord.Create(val: Integer); begin Red := val; end; procedure TMyRecord.printRed; begin writeln('Red: ', Red); end;
class abstract	Classes, and not just methods, can be declared as abstract. type TAbstractClass = class abstract procedure SomeProcedure; end;
class sealed	Classes marked as sealed cannot be inherited from. type TAbstractClass = class sealed procedure SomeProcedure; end;
class const	Classes can now have class constants -- a constant value associated with the class itself and not an instance of the class. type TClassWithConstant = class public const SomeConst = 'This is a class constant'; end; procedure TForm1.FormCreate(Sender: TObject); begin ShowMessage(TClassWithConstant.SomeConst); end;
class type	A class can now contain a type declaration that is usable only within that class. type TClassWithClassType = class private type TRecordWithinAClass = record SomeField: string; end; public class var RecordWithinAClass: TRecordWithinAClass; end; ... procedure TForm1.FormCreate(Sender: TObject); begin TClassWithClassType.RecordWithinAClass.SomeField := 'This is a field of a class type declaration'; ShowMessage(TClassWithClassType.RecordWithinAClass.SomeField); end;
class var	A class can also have a class variable, applicable only to the class and not an instance of the class. See "class type" for an example.
class property	A class can have a class property, which is a property that applies only to the class reference and not to an instance of a class.  The accessors for the class property must be either class methods or class variables. See the example in "static class methods" below.
nested classes	Type declarations can be nested within class declarations. They present a way to keep conceptually related types together, and to avoid name collisions. type TOuterClass = class strict private MyField: Integer; public type TInnerClass = class public MyInnerField: Integer; procedure InnerProc; end; procedure OuterProc; end; procedure TOuterClass.TInnerClass.InnerProc; begin ... end;
final methods	A virtual method that you override can now be marked final, preventing derived classes from overriding that method. TAbstractClass = classabstract public procedure Bar; virtual; end; TSealedClass = classsealed(TAbstractClass) public procedure Bar; override; end; TFinalMethodClass = class(TAbstractClass) public procedure Bar; override; final; end;
sealed methods	Classes marked as sealed cannot be descended from. See the example in 'final methods'.
static class methods	Classes can have static class methods -- i.e. methods that can be called from a class type. Class static methods can be accessed without an object reference. Unlike ordinary class methods, class static methods have no Self parameter at all. They also cannot access any instance members. (They still have access to class fields, class properties, and class methods.) Also unlike class methods, class static methods cannot be declared virtual. type TMyClass = class strict private class var FX: Integer; strict protected // Note: accessors for class properties must be declared class static. class function GetX: Integer; static; class procedure SetX(val: Integer); static; public class property X: Integer read GetX write SetX; class procedure StatProc(s: String); static; end; TMyClass.X := 17; TMyClass.StatProc('Hello');
for-in loop	Delphi 2007 for Win32 supports for-element-in-collection style iteration over containers. The following container iteration patterns are recognized by the compiler: for Element in ArrayExpr do Stmt; for Element in StringExpr do Stmt; for Element in SetExpr do Stmt; for Element in CollectionExpr do Stmt;