Python 設計模式之 單例模式

Python單例模式是做為"全局變量"的替代品出現的。所以它具有全局變量的特點：全局可見、貫穿應用程序的整個生命期，保證在程序運行中，某個類只存在一個實例，所以通常不希望類中的構造函數被調用。

Python:

class Single(object):
instance = None
#
def __init__(self):
pass
#
def getInstance(self):
if Single.instance == None:
Single.instance = Single()
return Single.instance
#
def printSelf(self):
if Single.instance != None:
print Single.instance

s = Single()
s1 = s.getInstance()
s2 = s.getInstance()
s1.printSelf()
s2.printSelf()

C++:

Single.h

ifndef __SINGLE_H
#define __SINGLE_H

class Single
{
private:
static Single *instance;

Single();

public:
static Single* getInstance();
void printSelf();
};

#endif

Single.cpp

#include "Single.h"
#include <iostream>

Single* Single::instance = NULL;

Single::Single()
{
}

Single* Single::getInstance()
{
if (!instance)
instance = new Single;

return instance;
}

void Single::printSelf()
{
if (instance)
std::cout << instance << std::endl;
}

#include "Single.h"

int main()
{
Single::getInstance()->printSelf();
Single *sin = Single::getInstance();
sin->printSelf();
return 0;
}

《Python核心編程 第二版》.(Wesley J. Chun ).[高清PDF中文版] http://www.linuxidc.com/Linux/2013-06/85425.htm

《Python開發技術詳解》.( 周偉,宗傑).[高清PDF掃描版+隨書視頻+代碼] http://www.linuxidc.com/Linux/2013-11/92693.htm

Python腳本獲取Linux系統信息 http://www.linuxidc.com/Linux/2013-08/88531.htm

在Ubuntu下用Python搭建桌面算法交易研究環境 http://www.linuxidc.com/Linux/2013-11/92534.htm

Python 語言的發展簡史 http://www.linuxidc.com/Linux/2014-09/107206.htm

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