Delphi 2009 泛型容器单元(Generics.Collections)[2]: TQueue

TQueue 和 TStack, 一个是队列列表, 一个是堆栈列表; 一个是先进先出, 一个是先进后出.

TQueue 主要有三个方法、一个属性:
Enqueue(入列)、Dequeue(出列)、Peek(查看下一个要出列的元素);
Count(元素总数).

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本例效果图:

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代码文件:

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unit Unit1;



interface



uses

  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,

  Dialogs, StdCtrls;



type

  TForm1 = class(TForm)

    Memo1: TMemo;

    Button1: TButton;

    Button2: TButton;

    Button3: TButton;

    procedure FormCreate(Sender: TObject);

    procedure FormDestroy(Sender: TObject);

    procedure Button1Click(Sender: TObject);

    procedure Button2Click(Sender: TObject);

    procedure Button3Click(Sender: TObject);

  end;



var

  Form1: TForm1;



implementation



{$R *.dfm}



uses Generics.Collections; {Delphi 2009 新增的泛型容器单元}



type

  TRec = record

    Name: string;

    Age: Word;

  end;



var

  Queue: TQueue<TRec>;  {定义一个泛型 TQueue 类, 这指定了要用于上面定义的 TRec 记录}



{建立}

procedure TForm1.FormCreate(Sender: TObject);

begin

  Queue := TQueue<TRec>.Create;



  Memo1.Clear;

  Button1.Caption := Button1.Caption + ' 入列';

  Button2.Caption := Button2.Caption + ' 出列';

  Button3.Caption := Button3.Caption + ' 下一个出列的...';

end;



{释放}

procedure TForm1.FormDestroy(Sender: TObject);

begin

  Queue.Free;

end;



{入列: Enqueue}

procedure TForm1.Button1Click(Sender: TObject);

var

  rec: TRec;

begin

  rec.Name := StringOfChar(Char(65 + Random(26)), 3);

  rec.Age := Random(150);

  Queue.Enqueue(rec);

  Text := Format('当前队列成员总数: %d', [Queue.Count]);



  {让 Memo1 配合显示}

  Memo1.Lines.Add(Format('%s, %d', [rec.Name, rec.Age]));

end;



{出列: Dequeue}

procedure TForm1.Button2Click(Sender: TObject);

var

  rec: TRec;

begin

  if Queue.Count = 0 then Exit;

  rec := Queue.Dequeue;

  ShowMessage(Format('%s, %d', [rec.Name, rec.Age]));

  Text := Format('当前队列成员总数: %d', [Queue.Count]);



  {让 Memo1 配合显示}

  Memo1.Lines.Delete(0);

end;



{下一个出列的元素: Peek}

procedure TForm1.Button3Click(Sender: TObject);

var

  rec: TRec;

begin

  if Queue.Count = 0 then Exit;

  rec := Queue.Peek;

  ShowMessage(Format('%s, %d', [rec.Name, rec.Age]));

end;



end.


 
   

窗体文件:

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object Form1: TForm1

  Left = 0

  Top = 0

  Caption = 'Form1'

  ClientHeight = 147

  ClientWidth = 284

  Color = clBtnFace

  Font.Charset = DEFAULT_CHARSET

  Font.Color = clWindowText

  Font.Height = -11

  Font.Name = 'Tahoma'

  Font.Style = []

  OldCreateOrder = False

  Position = poDesktopCenter

  OnCreate = FormCreate

  OnDestroy = FormDestroy

  PixelsPerInch = 96

  TextHeight = 13

  object Memo1: TMemo

    Left = 0

    Top = 0

    Width = 121

    Height = 147

    Align = alLeft

    Font.Charset = DEFAULT_CHARSET

    Font.Color = clWindowText

    Font.Height = -13

    Font.Name = 'Courier New'

    Font.Style = []

    Lines.Strings = (

      'Memo1')

    ParentFont = False

    ScrollBars = ssBoth

    TabOrder = 0

    ExplicitHeight = 201

  end

  object Button1: TButton

    Left = 127

    Top = 21

    Width = 146

    Height = 25

    Caption = 'Button1'

    TabOrder = 1

    OnClick = Button1Click

  end

  object Button2: TButton

    Left = 127

    Top = 61

    Width = 146

    Height = 25

    Caption = 'Button2'

    TabOrder = 2

    OnClick = Button2Click

  end

  object Button3: TButton

    Left = 127

    Top = 99

    Width = 146

    Height = 25

    Caption = 'Button3'

    TabOrder = 3

    OnClick = Button3Click

  end

end