泛型容器单元(Generics.Collections)[2]: TQueue<T> 队列列表

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).

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.

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