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add command
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‎README.md‎

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[责任链模式 Chain of Responsibility](doc/15-责任链.md)
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命令模式 Command
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[命令模式 Command](doc/16-命令.md)
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解释器模式 Interpreter
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‎code/15_command/15_command.sln‎

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Microsoft Visual Studio Solution File, Format Version 12.00
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# Visual Studio Version 16
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VisualStudioVersion = 16.0.29215.179
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MinimumVisualStudioVersion = 10.0.40219.1
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Project("{8BC9CEB8-8B4A-11D0-8D11-00A0C91BC942}") = "15_command", "15_command.vcxproj", "{37C48A70-F43B-4ED9-A0A0-377C11BF00A6}"
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EndProject
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Global
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GlobalSection(SolutionConfigurationPlatforms) = preSolution
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Debug|x64 = Debug|x64
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Debug|x86 = Debug|x86
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Release|x64 = Release|x64
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Release|x86 = Release|x86
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EndGlobalSection
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GlobalSection(ProjectConfigurationPlatforms) = postSolution
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{37C48A70-F43B-4ED9-A0A0-377C11BF00A6}.Debug|x64.ActiveCfg = Debug|x64
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{37C48A70-F43B-4ED9-A0A0-377C11BF00A6}.Debug|x64.Build.0 = Debug|x64
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{37C48A70-F43B-4ED9-A0A0-377C11BF00A6}.Debug|x86.ActiveCfg = Debug|Win32
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{37C48A70-F43B-4ED9-A0A0-377C11BF00A6}.Debug|x86.Build.0 = Debug|Win32
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{37C48A70-F43B-4ED9-A0A0-377C11BF00A6}.Release|x64.ActiveCfg = Release|x64
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{37C48A70-F43B-4ED9-A0A0-377C11BF00A6}.Release|x64.Build.0 = Release|x64
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{37C48A70-F43B-4ED9-A0A0-377C11BF00A6}.Release|x86.ActiveCfg = Release|Win32
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{37C48A70-F43B-4ED9-A0A0-377C11BF00A6}.Release|x86.Build.0 = Release|Win32
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EndGlobalSection
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GlobalSection(SolutionProperties) = preSolution
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HideSolutionNode = FALSE
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EndGlobalSection
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GlobalSection(ExtensibilityGlobals) = postSolution
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SolutionGuid = {2AA1AD58-F91F-45CF-ADCB-DDC21BA0091C}
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EndGlobalSection
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EndGlobal

‎code/15_command/client.cpp‎

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#include "command_types.h"
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int main() {
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Receiver* reciver1 = new MiCenter;
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Receiver* reciver2 = new ZigBee;
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list<Command*> list;
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Command* command1 = new SendMessage(reciver1,true);
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Command* command2 = new TurnOn(reciver2);
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Command* command3 = new SendMessage(reciver1, false);
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Command* command4 = new TurnOff(reciver2);
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Command* command5 = new TurnOff(reciver2);
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list.push_back(command1);
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list.push_back(command2);
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list.push_back(command3);
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list.push_back(command4);
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list.push_back(command5);
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Invoker* invoker = new BodySensor(list);
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invoker->invoke();
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return 0;
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}

‎code/15_command/command_types.h‎

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#pragma once
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#include <iostream>
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#include <list>
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using namespace std;
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class Command {
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public:
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virtual void execute() = 0;
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};
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class Receiver {
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public:
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virtual void action() = 0;
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};
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class Invoker {
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public:
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virtual void invoke() = 0;
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};
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class MiCenter : public Receiver {
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public:
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void action() {
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cout << "[MiCenter]Stored detect people event" << endl;
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}
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};
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class ZigBee :public Receiver {
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public:
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ZigBee() :state(false) {}
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void action() {
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if (state) {
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cout << "Current state is turn on, so turn off now.\n" << endl;
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}
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else {
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cout << "Current state is turn off, so turn on now.\n" << endl;
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}
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state = !state;
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}
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bool getState() {
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return state;
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}
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private:
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bool state;
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};
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class SendMessage : public Command {
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public:
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SendMessage(Receiver* receiver,bool hasPerson) :m_hasPerson(hasPerson),m_receiver(receiver) {
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}
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void execute() {
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cout << (m_hasPerson?"Detect people now.":"Not detect people in recent minutes.")<< endl;
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if (m_receiver)
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m_receiver->action();
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}
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private:
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bool m_hasPerson;
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Receiver* m_receiver;
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};
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class TurnOn : public Command {
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public:
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TurnOn(Receiver* receiver) :m_receiver(receiver) {
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}
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void execute() {
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if (m_receiver) {
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ZigBee* receiver = static_cast<ZigBee*>(m_receiver);
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if (receiver && receiver->getState() == false)
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m_receiver->action();
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else
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cout << "Reciver[ZigBee] already turn on, so ignore" << endl;
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}
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}
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private:
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Receiver* m_receiver;
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};
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class TurnOff : public Command {
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public:
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TurnOff(Receiver* receiver) :m_receiver(receiver) {
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}
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void execute() {
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if (m_receiver) {
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ZigBee* receiver = static_cast<ZigBee*>(m_receiver);
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if (receiver && receiver->getState())
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m_receiver->action();
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else
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cout << "Reciver[ZigBee] already turn off, so ignore" << endl;
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}
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}
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private:
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Receiver* m_receiver;
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};
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class BodySensor : public Invoker {
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public:
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BodySensor(list<Command*>& cmdlist):cmdlist_ptr(cmdlist){}
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void invoke() {
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list<Command*>::const_iterator iter = cmdlist_ptr.begin();
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while (iter != cmdlist_ptr.end()) {
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(*iter)->execute();
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iter++;
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}
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}
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private:
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list<Command*> cmdlist_ptr;
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};

‎code/15_command/result.png‎

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‎doc/16-命令.md‎

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# 命令
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将一个请求封装为一个对象，从而可用不同的请求对客户进行参数化，对请求排队或者记录请求日志，以及支持可撤销的操作。
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## UML
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* Command(抽象命令类): 是一个抽象类，声明了用于执行命令的接口execute()
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* ConcreteCommnad(具体命令类): 具体的命令类，实现了执行命令的接口execute()，它对应具体的接收者对象，将接收者（Receiver）的动作action()绑定其中。在execu()方法中将调用接收者的动作action()
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* Invoker(调用者): 请求的发送者，通过命令对象来执行请求。一个调用者不需要在设计时确定其接收者，所以调用者通过聚合，与命令类产生关联
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* Receiver(接收者): 实现处理请求的具体操作（action）
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![figure15_command](img/figure15_command.png)
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## 优缺点
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* 优点
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* 降低系统耦合度，将命令的请求者与接收者分离解耦，请求者和发送者不存在直接关联，各自独立互不影响
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* 便于扩展：新的命令很容易加入到系统中，且符合开闭原则
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* 较容易实现命令队列或宏命令
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* 为请求的撤销和回复操作提供了一种设计实现方案
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* 缺点
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* 命令模式可能导致系统中有过多的具体命令类，增加了系统中对象的数量
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## 使用场景
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* 系统需要将请求发送者和接收者解耦，使得发送者和接收者互不影响
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* 系统需要在不同时间指定请求、将请求排队和执行请求
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* 系统需要支持命令的撤销和恢复操作
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* 系统需要将一组操作组合在一起形成宏命令
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## 用例
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小米智能家居有以下应用场景:
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下班回家,打开门, 人体感应器识别到人体,发送消息到小米网关,网关打开智能插座,点亮灯
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[code](../code/15_command)
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```c++
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// command_types.h
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#pragma once
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#include <iostream>
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#include <list>
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using namespace std;
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class Command {
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public:
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virtual void execute() = 0;
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};
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class Receiver {
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public:
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virtual void action() = 0;
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};
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class Invoker {
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public:
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virtual void invoke() = 0;
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};
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class MiCenter : public Receiver {
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public:
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void action() {
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cout << "[MiCenter]Stored detect people event" << endl;
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}
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};
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class ZigBee :public Receiver {
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public:
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ZigBee() :state(false) {}
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void action() {
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if (state) {
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cout << "Current state is turn on, so turn off now.\n" << endl;
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}
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else {
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cout << "Current state is turn off, so turn on now.\n" << endl;
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}
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state = !state;
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}
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bool getState() {
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return state;
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}
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private:
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bool state;
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};
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class SendMessage : public Command {
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public:
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SendMessage(Receiver* receiver,bool hasPerson) :m_hasPerson(hasPerson),m_receiver(receiver) {
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}
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void execute() {
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cout << (m_hasPerson?"Detect people now.":"Not detect people in recent minutes.")<< endl;
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if (m_receiver)
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m_receiver->action();
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}
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private:
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bool m_hasPerson;
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Receiver* m_receiver;
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};
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class TurnOn : public Command {
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public:
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TurnOn(Receiver* receiver) :m_receiver(receiver) {
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}
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void execute() {
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if (m_receiver) {
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ZigBee* receiver = static_cast<ZigBee*>(m_receiver);
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if (receiver && receiver->getState() == false)
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m_receiver->action();
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else
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cout << "Reciver[ZigBee] already turn on, so ignore" << endl;
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}
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}
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private:
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Receiver* m_receiver;
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};
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class TurnOff : public Command {
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public:
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TurnOff(Receiver* receiver) :m_receiver(receiver) {
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}
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void execute() {
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if (m_receiver) {
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ZigBee* receiver = static_cast<ZigBee*>(m_receiver);
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if (receiver && receiver->getState())
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m_receiver->action();
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else
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cout << "Reciver[ZigBee] already turn off, so ignore" << endl;
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}
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}
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private:
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Receiver* m_receiver;
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};
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class BodySensor : public Invoker {
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public:
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BodySensor(list<Command*>& cmdlist):cmdlist_ptr(cmdlist){}
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void invoke() {
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list<Command*>::const_iterator iter = cmdlist_ptr.begin();
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while (iter != cmdlist_ptr.end()) {
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(*iter)->execute();
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iter++;
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}
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}
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private:
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list<Command*> cmdlist_ptr;
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};
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```
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```c++
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// client.cpp
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#include "command_types.h"
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int main() {
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Receiver* reciver1 = new MiCenter;
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Receiver* reciver2 = new ZigBee;
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list<Command*> list;
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Command* command1 = new SendMessage(reciver1,true);
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Command* command2 = new TurnOn(reciver2);
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Command* command3 = new SendMessage(reciver1, false);
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Command* command4 = new TurnOff(reciver2);
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Command* command5 = new TurnOff(reciver2);
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list.push_back(command1);
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list.push_back(command2);
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list.push_back(command3);
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list.push_back(command4);
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list.push_back(command5);
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Invoker* invoker = new BodySensor(list);
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invoker->invoke();
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return 0;
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}
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```

‎doc/img/figure15_command.png‎

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‎doc/uml/15_command.pu‎

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@startuml "figure15_command"
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caption figure 16: Command
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class Command{
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+ execute(): void
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}
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class ConcreteCommand{}
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class Invoker{
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- commandList: List<Command>
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+ invoke(): void
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}
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class Receiver{
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+ action(): void
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}
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class Client{}
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Command <|-- ConcreteCommand
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Invoker o-right- Command
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Receiver <-right- ConcreteCommand
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Client .up.> Invoker
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Client ..> ConcreteCommand
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@enduml

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