Delphi实现Singleton模式

王朝delphi·作者佚名  2006-01-09
窄屏简体版  字體: |||超大  

单例模式用于限制进程中只有一个某个类的对象,本例的Singleton是一个线程实例,在每一个时钟到达时检测是否到达某个时刻(本例的时刻存于Ini文件中),如果到达则产生一个线程,但是如果在这个线程完成其任务前又到达一个时钟,则有可能会产生多个线程执行任务,以致出现混乱,所以考虑使用Singleton模式解决这个问题(当然还有其他解决方案,但本例使用的是Singleton)。

核心代码如下:

//timer单元

procedure TService1.Timer_mainTimer(Sender: TObject);

var

mystringlist:TStringList;

SearchRec: TSearchRec;

nowtime :string;

begin

try

DateTimeToString(nowtime,'hh:nn',now);

if LeftStr(nowtime,4)=LeftStr(GetMSG('GAME','下发时间',theexename+'.ini'),4) then

begin

//创建发送线程

Global_Instance:=TSendThread.getInstance;

//////////////

end;

except

on e: Exception do

begin

mystringlist:=TStringList.Create;

if FileExists(ExtractFilePath(Paramstr(0))+'Err.txt') then

mystringlist.LoadFromFile(ExtractFilePath(Paramstr(0))+'Err.txt');

mystringlist.Add('('+DateTimeToStr(Now)+')[创建线程出错:]'+E.Message);

mystringlist.SaveToFile(ExtractFilePath(Paramstr(0))+'Err.txt');

mystringlist.Free;

if FindFirst(ExtractFilePath(Paramstr(0))+'Err.txt', faAnyFile, SearchRec)=0 then

begin

if SearchRec.Size>5000000 then

begin

RenameFile(ExtractFilePath(Paramstr(0))+'Err.txt',ansireplacestr(ExtractFilePath(Paramstr(0))+'Err.txt','.txt',FormatDateTime('yyyy-MM-dd hh-mm-ss',now)+'.txt'));

end;

end;

end;

end;

end;

//线程单元

unit Unit_Send ;

interface

uses

SysUtils, Classes,StrUtils,main;

type

TSendThread = class(TThread)

public

constructor Create(CreateSuspended: Boolean);

destructor Destroy; override;

class function getInstance:TSendThread;

procedure joke;

protected

procedure Execute; override;

end;

var

Global_Instance:TSendThread;

implementation

uses DB;

class function TSendThread.getInstance:TSendThread;

begin

if Global_Instance=nil then

begin

Global_Instance:=TSendThread.Create(false);

end;

Result:=Global_Instance;

end;

constructor TSendThread.Create(CreateSuspended: Boolean);

begin

if Global_Instance=nil then

begin

inherited Create(CreateSuspended);

FreeOnTerminate:=true ;

end

else

raise Exception.CreateFmt('Can not create more than one TSendThread instance!',[SysErrorMessage(0)]);

end;

destructor TSendThread.Destroy;

begin

inherited Destroy;

end;

procedure TSendThread.joke;

begin

end;

procedure TSendThread.Execute;

var

theuser:TUserInfo;

tmpSql:string;

begin

//执行任务

//处理定时下发 '+GameInfo.mainusertable+'

tmpSql:='select * from '+mainusertable+' where destroy=0 order by id';

Service1.ADOQuery_send.Connection:=conn_Server;

SQLQuery(Service1.ADOQuery_send,tmpSql);

while (not Service1.ADOQuery_send.Eof) and (not Terminated) do

begin

theuser.SeqID:='0';

theuser.UID:='';

theuser.Spc:=GetMSG('PARAMETER','Spcode',theexename+'.ini');

theuser.RecordID:='0';

theuser.Mob:=Service1.ADOQuery_send.FieldByname('mobile').AsString;

AutoJoke(theuser);

Service1.ADOQuery_send.Next;

end;

Sleep(600001);

Global_Instance:=nil;

Terminate;

//任务完成

end;

end.

-----------------------------------------

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