TMyList = class(TObject) FList: PPointerList;end;既然是一个列表, 应该有 Count 字段:
TMyList = class(TObject) FList: PPointerList; FCount: Integer;end;TList 类还有一个 FCapacity 字段. 譬如当前列表中有 10 个元素时, 其实列表已经提前申请出更多位置, 这样就不必每次添加每次申请内存, 从而提高了效率. 这个 FCapacity 字段就表示已申请的可放置元素位置的总数.
TMyList = class(TObject) FList: PPointerList; FCount: Integer; FCapacity: Integer;end;它们都应该是私有的:
TMyList = class(TObject)private FList: PPointerList; FCount: Integer; FCapacity: Integer;publicend;应该用属性操作它们:
unit Unit1;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs;type TForm1 = class(TForm) end;{--------------------------------} TMyList = class(TObject) private FList: PPointerList; FCount: Integer; FCapacity: Integer; public property Capacity: Integer; {光标放在属性上, 执行 Shift+Ctrl+C, 自动建立属性} property Count: Integer; property List: PPointerList; end;{--------------------------------}var Form1: TForm1;implementation{$R *.dfm}end. 自动建立后的属性: unit Unit1;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs;type TForm1 = class(TForm) end;{--------------------------------} TMyList = class(TObject) private FList: PPointerList; FCount: Integer; FCapacity: Integer; procedure SetCapacity(const Value: Integer); procedure SetCount(const Value: Integer); procedure SetList(const Value: PPointerList); public property Capacity: Integer read FCapacity write SetCapacity; property Count: Integer read FCount write SetCount; property List: PPointerList read FList write SetList; end;{--------------------------------}var Form1: TForm1;implementation{$R *.dfm}{ TMyList }procedure TMyList.SetCapacity(const Value: Integer);begin FCapacity := Value;end;procedure TMyList.SetCount(const Value: Integer);begin FCount := Value;end;procedure TMyList.SetList(const Value: PPointerList);begin FList := Value;end;end. 在 TList 中, SetCount 和 SetCapacity 方法都是放在 protected 区以供子类使用, 这里暂时不考虑继承的问题, 就让它们先在 private 区吧; 不过 List 属性应该是只读的, 它就是那个核心数组的指针, 对它的赋值应该通过更多其他的方法. 修改如下: unit Unit1;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs;type TForm1 = class(TForm) end;{--------------------------------} TMyList = class(TObject) private FList: PPointerList; FCount: Integer; FCapacity: Integer; procedure SetCapacity(const Value: Integer); procedure SetCount(const Value: Integer); public property Capacity: Integer read FCapacity write SetCapacity; property Count: Integer read FCount write SetCount; property List: PPointerList read FList; end;{--------------------------------}var Form1: TForm1;implementation{$R *.dfm}{ TMyList }procedure TMyList.SetCapacity(const Value: Integer);begin FCapacity := Value;end;procedure TMyList.SetCount(const Value: Integer);begin FCount := Value;end;end. 作为一个列表, 最起码应该有 Add、Delete、Clear 方法. Add 方法的参数应该是一个指针(TList 就是存放指针的吗), 如果需要同时返回元素的位置, 应该定义成函数; Delete 是删除指定位置上的元素, 参数是个位置号; Clear 是清除列表, 对象释放(Destroy)时也应该执行此过程. 综上所述, 修改如下: unit Unit1;interfaceuses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs;type TForm1 = class(TForm) end;{--------------------------------} TMyList = class(TObject) private FList: PPointerList; FCount: Integer; FCapacity: Integer; procedure SetCapacity(const Value: Integer); procedure SetCount(const Value: Integer); public destructor Destroy; override; {覆盖父类的 Destroy 方法} function Add(Item: Pointer): Integer; procedure Clear; {在 TList 中这是个虚方法, 以备子类覆盖} procedure Delete(Index: Integer); property Capacity: Integer read FCapacity write SetCapacity; property Count: Integer read FCount write SetCount; property List: PPointerList read FList; end;{--------------------------------}var Form1: TForm1;implementation{$R *.dfm}{ TMyList }function TMyList.Add(Item: Pointer): Integer;beginend;procedure TMyList.Clear;beginend;procedure TMyList.Delete(Index: Integer);beginend;destructor TMyList.Destroy;begin Clear; {在类释放时同时清除列表} inherited; {在 TList 中没有这句, 大概是因为它的父类也没什么可继承的}end;procedure TMyList.SetCapacity(const Value: Integer);begin FCapacity := Value;end;procedure TMyList.SetCount(const Value: Integer);begin FCount := Value;end;end. 为了让代码更清晰, 还是把这个类相关的所有代码放到一个独立的单元吧(新建一个单元, 我们把它保存为: MyList.pas). 因为 MaxListSize、TPointerList、PPointerList 都是在 Classes 单元定义的, 为了省略 uses Classes, 在 MyList 单元中重新做了定义. unit MyList;interfaceconst MaxListSize = Maxint div 16;type PPointerList = ^TPointerList; TPointerList = array[0..MaxListSize - 1] of Pointer; TMyList = class(TObject) private FList: PPointerList; FCount: Integer; FCapacity: Integer; procedure SetCapacity(const Value: Integer); procedure SetCount(const Value: Integer); public destructor Destroy; override; function Add(Item: Pointer): Integer; procedure Clear; procedure Delete(Index: Integer); property Capacity: Integer read FCapacity write SetCapacity; property Count: Integer read FCount write SetCount; property List: PPointerList read FList; end;implementation{ TMyList }function TMyList.Add(Item: Pointer): Integer;beginend;procedure TMyList.Clear;beginend;procedure TMyList.Delete(Index: Integer);beginend;destructor TMyList.Destroy;begin Clear; inherited;end;procedure TMyList.SetCapacity(const Value: Integer);beginend;procedure TMyList.SetCount(const Value: Integer);beginend;end. 至此, 类的轮廓已经出来, 该实现一下这些方法了.