文章目錄
-
- 1. 什麼是簡單工廠模式?
- 2. 簡單工廠模式的适用場景?
-
- 2.1 優點
- 2.2 缺點
- 3. 怎樣使用簡單工廠模式?
-
- 3.1 方法
- 3.2 UML類圖
- 4. 執行個體
-
- 4.1 結果(結論先行)
- 4.2 具體實作
-
- 4.2.1 簡單工廠的靜态接口
- 4.2.2 四則運算符繼承體系代碼
1. 什麼是簡單工廠模式?
當出現批量化的産品時,使用單獨的類建立每個産品,實作去執行個體化對象。
2. 簡單工廠模式的适用場景?
優缺點有參考這篇部落格:簡單工廠和工廠方法模式
2.1 優點
1、降低了客戶與具體實作的耦合(相較不使用簡單工廠而言)。
封裝了細節,客戶隻需調用工廠接口,不必關心如何建立産品,隻關心使用産品;
2.2 缺點
1、工廠類對産品的耦合較強
集中了所有産品的建立邏輯,子產品與子產品之間耦合在一個類裡。 工廠崩、系統也崩;
2、違反“開放-關閉原則”
添加新産品,除了添加新産品代碼外,還需要修改工廠邏輯,添加分支處理;
3. 怎樣使用簡單工廠模式?
3.1 方法
以四則運算器工廠為例:
1、簡單工廠類提供靜态方法,通過
swich...case...
生成對應運算器執行個體。
傳回運算器的基類,将分支的子類指針指派給了基類,實作客戶與具體産品的解耦。
2、提供運算器基類,實作通用方法,提供抽象的結果純虛接口
getResult()
。
3、加減乘除子類分别實作
getResult()
接口,應用了多态運作時生成對象的特點,通過基類指針調用該接口,完成用戶端加減乘除功能的實作。
3.2 UML類圖
4. 執行個體
4.1 結果(結論先行)
4.1.1 main.cpp
#include "Operation.h"
#include "OperationFactory.h"
using namespace std;
void test()
{
double numA = 20, numB = 10;
cout << "A = " << numA << "\tB = " << numB << endl;
Operation* oper = OperationFactory::createOperation('+');
oper->setNumberA(numA);
oper->setNumberB(numB);
cout << "add result = " << oper->getResult() << endl;
oper = OperationFactory::createOperation('-');
oper->setNumberA(numA);
oper->setNumberB(numB);
cout << "sub result = " << oper->getResult() << endl;
oper = OperationFactory::createOperation('*');
oper->setNumberA(numA);
oper->setNumberB(numB);
cout << "mul result = " << oper->getResult() << endl;
oper = OperationFactory::createOperation('/');
oper->setNumberA(numA);
oper->setNumberB(numB);
cout << "div result = " << oper->getResult() << endl;
}
int main()
{
test();
system("pause");
return 0;
}
4.2 具體實作
4.2.1 簡單工廠的靜态接口
1、OperationFactory.h
#pragma once
#include "Operation.h"
#include "OperationAdd.h"
#include "OperationMul.h"
#include "OperationDiv.h"
#include "OperationSub.h"
class OperationFactory
{
public:
static Operation* createOperation(char sOperate);
};
Operation* OperationFactory::createOperation(char sOperate)
{
Operation* oper = nullptr;
switch (sOperate)
{
case '+':
oper = new OperationAdd();
break;
case '-':
oper = new OperationSub();
break;
case '*':
oper = new OperationMul();
break;
case '/':
oper = new OperationDiv();
break;
default:
break;
}
return oper;
}
4.2.2 四則運算符繼承體系代碼
1、Operation.h
#pragma once
#include <iostream>
class Operation
{
public:
Operation() {}
virtual ~Operation() {}
virtual double getResult() = 0;
double getNumberA() { return m_numberA; }
double getNumberB() { return m_numberB; }
void setNumberA(const double& num) { m_numberA = num; }
void setNumberB(const double& num) { m_numberB = num; }
protected:
double m_numberA{ 0 };
double m_numberB{ 0 };
};
2、OperationAdd.h
#pragma once
#include "Operation.h"
class OperationAdd :
public Operation
{
public:
OperationAdd() {}
virtual ~OperationAdd() {}
double getResult() override { return m_numberA + m_numberB; }
};
3、OperationSub.h
#pragma once
#include "Operation.h"
class OperationSub :
public Operation
{
public:
OperationSub() {}
virtual ~OperationSub() {}
double getResult() override { return m_numberA - m_numberB; }
};
4、OperationMul.h
#pragma once
#include "Operation.h"
class OperationMul :
public Operation
{
public:
OperationMul() {}
virtual ~OperationMul() {}
double getResult() override { return m_numberA * m_numberB; }
};
5、OperationDiv.h
#pragma once
#include "Operation.h"
class OperationDiv :
public Operation
{
public:
OperationDiv() {}
virtual ~OperationDiv() {}
double getResult() override
{
double result = 0;
if (m_numberB == 0)
throw new std::exception("除數不能為0。");
result = m_numberA / m_numberB;
return result;
}
};
此為《大話設計模式》學習心得系列 P9~~
簡單工廠進階一:《大話設計模式》C++實作:08 工廠模式
簡單工廠進階二:《大話設計模式》C++實作:01 簡單工廠模式(優化,使用宏注冊工廠)