[C++知识库]01简单工厂模式（c++实现）

简单工厂模式

主要用于创建对象。新添加类时，不会影响以前的系统代码。核心思想是用一个工厂来
根据输入的条件产生不同的类，然后根据不同类的 virtual 函数得到不同的结果。

优点:适用于不同情况创建不同的类时
缺点：客户端必须要知道基类和工厂类，耦合性差

Opeartion.h

#ifndef CHAPTER1_OPERATION_H
#define CHAPTER1_OPERATION_H

#pragma once
#include <iostream>

class Operation{
public:
    Operation();
    virtual double GetResult();
    void SetNumberA(double value);
    void SetNumberB(double value);
    double GetNumberA();
    double GetNumberB();

protected:
    double m_NumberA;
    double m_NumberB;
};


#endif //CHAPTER1_OPERATION_H

Operation.cpp

#include "Operation.h"

Operation::Operation() :m_NumberA(0),m_NumberB(0){}

void Operation::SetNumberA(double value) {
    this->m_NumberA = value;
}

void Operation::SetNumberB(double value) {
    this->m_NumberB = value;
}

double Operation::GetNumberA(){
    return m_NumberA;
}

double Operation::GetNumberB() {
    return m_NumberB;
}

double Operation::GetResult() {
    double result = 0;
    return result;
}

OpeartionAdd.h

#ifndef CHAPTER1_OPERATIONADD_H
#define CHAPTER1_OPERATIONADD_H

#include "Operation.h"

class OperationAdd : public Operation{
public:
    OperationAdd();
    double GetResult() override;
};

#endif //CHAPTER1_OPERATIONADD_H

OpeartionAdd.cpp

#include "OperationAdd.h"

OperationAdd::OperationAdd() {
    std::cout << "operation of adding ..." << std::endl;
}

double OperationAdd::GetResult() {
    double result = m_NumberA + m_NumberB;
    return result;
}

OpeartionSub.h

#ifndef CHAPTER1_OPERATIONSUB_H
#define CHAPTER1_OPERATIONSUB_H

#include "Operation.h"

class OperationSub : public Operation{
public:
    OperationSub();
    double GetResult() override;
};

#endif //CHAPTER1_OPERATIONSUB_H

OpeartionSub.cpp

#include "OperationSub.h"

OperationSub::OperationSub() {
    std::cout << "operation of subing ..." << std::endl;
}

double OperationSub::GetResult(){
    double result = m_NumberA - m_NumberB;
    return result;
}

OperationMul.h

#ifndef CHAPTER1_OPERATIONMUL_H
#define CHAPTER1_OPERATIONMUL_H

#include "Operation.h"

class OperationMul : public Operation{
public:
    OperationMul();
    double GetResult() override;
};


#endif //CHAPTER1_OPERATIONMUL_H

OperationMul.cpp

#include "OperationMul.h"

OperationMul::OperationMul() {
    std::cout << "operation of muling ..." << std::endl;
}

double OperationMul::GetResult() {
    double result = m_NumberA * m_NumberB;
    return result;
}

OpeartionDiv.h

#ifndef CHAPTER1_OPERATIONDIV_H
#define CHAPTER1_OPERATIONDIV_H

#include "Operation.h"

class OperationDiv : public Operation{
public:
    OperationDiv();
    double GetResult() override;
};

#endif //CHAPTER1_OPERATIONDIV_H

OpeartionDiv.cpp

#include "OperationDiv.h"

OperationDiv::OperationDiv() {
    std::cout << "operation of diving ..." << std::endl;
}

double OperationDiv::GetResult() {
    if(m_NumberB==0){
        std::cout << "除数不能为0！" << std::endl;
    }
    double result = m_NumberA / m_NumberB;
    return  result;
}

OpeartionFactory.h

#ifndef CHAPTER1_OPERATIONFACTORY_H
#define CHAPTER1_OPERATIONFACTORY_H

#include "Operation.h"
#include "OperationAdd.h"
#include "OperationSub.h"
#include "OperationMul.h"
#include "OperationDiv.h"
#include "string"

class OperationFactory{
public:
    static Operation *CreatOperate(std::string operate);
};

#endif //CHAPTER1_OPERATIONFACTORY_H

OpeartionFactory.cpp

#include "OperationFactory.h"

Operation *OperationFactory::CreatOperate(std::string operate) {
    Operation *oper;
    if (operate == "+"){
        oper = new OperationAdd();
    }
    else if (operate == "-"){
        oper = new OperationSub();
    }
    else if (operate == "*"){
        oper = new OperationMul();
    }
    else{
        oper = new OperationDiv();
    }
    return oper;
}

main.cpp

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

int main() {
    std::string str[] = {"+","-","*","/"};
    Operation *oper;
    for (auto & i : str){
        oper = OperationFactory::CreatOperate(i);
        oper->SetNumberA(4);
        oper->SetNumberB(2);
        std::cout << oper->GetResult() << std::endl;
    }
    return 0;
}

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