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).

本例效果图:



代码文件:

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:

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