设计模式

命令模式

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命令模式

设计模式

Command模式也叫命令模式，是行为设计模式的一种。Command模式通过被称为Command的类封装了对目标对象的调用行为以及调用参数。

在面向对象的程序设计中，一个对象调用另一个对象，一般情况下的调用过程是：创建目标对象实例；设置词用参数；词用目标对象的方法。

但在有些情况下有必要使用一个专门的类对这种调用过程加以封装，我们把这种专门的类称作 command类。

整个调用过程比较繁杂，或者存在多处这种调用。这时，使用 Command类对该调用加以封装，便于功能的再利用。

调用前后需要对调用参数进行某些处理。调用前后需要进行某些额外处理，比如日志，缓存，记录历史操作等。

image-20201020230528330

Command

​ Command命令的抽象类

ConcreteCommand

​ Command命令的具体实现类

Receive

​ 需要被调用的目标对象

Invorker

​ 通过Invorker执行Command对象

适用于：

​ 是将一个请求封装成一个类，从而使你可用不同的请求对客户端进行参数化；对请求排队或者记录请求日志，以及支持可撤销请求的操作。

代码

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#include <iostream>
#include <list>

using namespace std;

class Doctor
{
public:
    void treat_eye()
    {
        cout << "医生 治疗 眼科病" << endl;
    }

    void treat_nose()
    {
        cout << "医生 治疗 鼻科病" << endl;
    }

    void treat_mouth()
    {
        cout << "医生 治疗 口腔科病" << endl;
    }
protected:
private:
};

class Command
{
public:
    virtual void treat() = 0;
protected:
private:
};

class CommandTreatEye : public Command
{
public:
    CommandTreatEye(Doctor* doctor)
    {
        m_doctor = doctor;
    }
    void treat()
    {
        m_doctor->treat_eye();
    }
protected:
private:
    Doctor* m_doctor;
};

class CommandTreatNose : public Command
{
public:
    CommandTreatNose(Doctor* doctor)
    {
        m_doctor = doctor;
    }
    void treat()
    {
        m_doctor->treat_nose();
    }
protected:
private:
    Doctor* m_doctor;
};

class Nurse
{
public:
    Nurse(Command* command)
    {
        m_command = command;
    }
    void SubmittedCase()//提交病例（提交命令）
    {
        m_command->treat();
    }
protected:
private:
    Command* m_command;
};

//护士长
class HeadNurse
{
public:
    HeadNurse()
    {
        m_list.clear();
    }
    void setCommand(Command* command)
    {
        m_list.push_back(command);
    }
    void SubmittedCase()//提交病例（提交命令）
    {
        for(auto command : m_list)
        {
            command->treat();
        }
    }
protected:
private:
    list<Command*> m_list;
};

int main()
{
    //1.医生直接看病
    /*
    Doctor* doctor = new Doctor;
    doctor->treat_eye();
    delete doctor;
    */

    //2.通过命令医生来看病
    /*
    Doctor* doctor = new Doctor;
    CommandTreatEye* commandtreateye = new CommandTreatEye(doctor);
    commandtreateye->treat();
    delete commandtreateye;
    delete doctor;
    */

    //3.通过护士提交病例实现医生看病
    /*
    Doctor* doctor = new Doctor;
    Command* command0 = new CommandTreatEye(doctor);
    //Command* command1 = new CommandTreatNose(doctor);//可以面向命令编程，实现客户端与命令的解耦合
    Nurse* nurse = new Nurse(command0);
    //Nurse* nurse = new Nurse(command1);
    nurse->SubmittedCase();
    delete nurse;
    delete command0;
    //delete command1;
    delete doctor;
    */

    //4.通过护士长批量下达命令
    Doctor* doctor = new Doctor;
    Command* command0 = new CommandTreatEye(doctor);
    Command* command1 = new CommandTreatNose(doctor);
    HeadNurse* headNurse = new HeadNurse;
    headNurse->setCommand(command0);
    headNurse->setCommand(command1);
    headNurse->SubmittedCase();
    delete headNurse;
    delete command0;
    delete command1;
    delete doctor;

    cout << "Hello world!" << endl;
    return 0;
}

输出：

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医生 治疗 眼科病
医生 治疗 鼻科病
Hello world!