创意网站案例,网页开发书籍,上海网页制作电话,成都网站建设网站建设哪家好引入#xff1a;以一个对数组的增删改查为例。通过命令模式可以对数组进行增删改查以及撤销回滚。
一、基本概念
命令模式有多种分法#xff0c;在本文中主要分为CommandMgr、Command、Receiver.
CommandMgr主要用于控制命令执行等操作、Command为具体的命令、Receiver为命…引入以一个对数组的增删改查为例。通过命令模式可以对数组进行增删改查以及撤销回滚。
一、基本概念
命令模式有多种分法在本文中主要分为CommandMgr、Command、Receiver.
CommandMgr主要用于控制命令执行等操作、Command为具体的命令、Receiver为命令具体要操作的对象。
总而言之增删改查就是具体的Command、Receiver就是数组、CommandMgr负责控制命令的执行与回滚等。
二、程序设计
以下代码可从github下载GitHub - laizilianglaiziliang/LearnCommandProject
1.Receiver
//Receiver_Array.h
#pragma once
#includevector
#includeoptional
#includeiostream
template class T
class Receiver_Array
{
private:std::vectorT* myArry;
public:~Receiver_Array(){}Receiver_Array() {myArry new std::vectorT();}Receiver_Array(std::vectorT* _myArry){if (_myArry){myArry new std::vectorT(*_myArry);}else{myArry new std::vectorT();}}bool add(const int pos, const T val){if (errorCheck(pos)){return false;}myArry-insert(pos myArry-begin(), val);return true;}bool del(const int pos){if (errorCheck(pos)){return false;}myArry-erase(pos myArry-begin());return true;}bool modify(const int pos, const T val){if (errorCheck(pos)){return false;}myArry-erase(pos myArry-begin());return true;}std::optionalT seek(const int pos){if (errorCheck(pos)){return std::nullopt;}return (*myArry)[pos];}bool errorCheck(const int pos){if (pos myArry-size()){printf( Operation Failed.Array Bounds Errors. );return true;}return false;}void display(){for (int i 0; i myArry-size(); i){std::cout (*myArry)[i] ;}std::cout std::endl;}
};
在本例子中Receiver_Array类是一个模板类可支持不同类型的数组。同时实现了对数组进行增删改查为不同的命令类提供了基础的功能。
2.Command
//Command.h
#pragma once
#include Receiver_Array.h
#includeoptional
#include memory
class Command
{
public: int m_iPos;bool m_bCanRevert;
public:Command(int _pos) : m_iPos(_pos), m_bCanRevert(true){}virtual ~Command(){}virtual bool execute() 0;virtual void* executeOther(){return nullptr;}virtual bool undo() 0;virtual bool redo() 0;
};
template class T
class AddCommand:public Command
{
private:std::shared_ptrReceiver_ArrayT m_Receiver_Array;T m_Val;
public:AddCommand() {}AddCommand(std::shared_ptrReceiver_ArrayT _receiver_Array, int _pos,const T _val) :Command( _pos), m_Receiver_Array(_receiver_Array), m_Val(_val){ }virtual ~AddCommand() {//if (m_Receiver_Array)//{// m_Receiver_Array-destory();// m_Receiver_Array nullptr;//}}bool execute() override{try{if (this-m_Receiver_Array-add(this-m_iPos, m_Val)){printf( Add Success.);return true;}printf( Add Fail.);return false;}catch(...){printf( Add Fail.);return false;}return true; }virtual bool undo() override{try{if (this-m_Receiver_Array-del(this-m_iPos)){printf( Undo Success.);return true;}}catch (...){}printf( Undo Fail.);return false;}virtual bool redo() override{if (execute()){printf( Redo Success.);return true;}printf( Redo Fail.);return false;}
};
template class T
class DelCommand :public Command
{
private:std::shared_ptrReceiver_ArrayT m_Receiver_Array;T m_Val;
public:DelCommand() {}DelCommand(std::shared_ptrReceiver_ArrayT _receiver_Array, int _pos) :Command(_pos), m_Receiver_Array(_receiver_Array){}virtual ~DelCommand(){//if (m_Receiver_Array)//{// m_Receiver_Array-destory();// m_Receiver_Array nullptr;//}}bool execute() override{try{std::optionalT val m_Receiver_Array-seek(m_iPos);if (val!std::nullopt this-m_Receiver_Array-del(this-m_iPos)){printf( Del Success.);m_Val val.value();return true;}printf( Del Fail.);return false;}catch (...){printf( Del Fail.);return false;}return true;}virtual bool undo() override{try{if (this-m_Receiver_Array-add(this-m_iPos, m_Val)){printf( Undo Success.);return true;}}catch (...){}printf( Undo Fail.);return false;}virtual bool redo() override{if (execute()){printf( Redo Success.);return true;}printf( Redo Fail.);return false;}
};
template class T
class ModifyCommand :public Command
{
private:std::shared_ptrReceiver_ArrayT m_Receiver_Array;T m_Val;
public:ModifyCommand() {}ModifyCommand(std::shared_ptrReceiver_ArrayT _receiver_Array, int _pos,const T _val) :Command(_pos), m_Receiver_Array(_receiver_Array), m_Val(_val){}virtual ~ModifyCommand(){//if (m_Receiver_Array)//{// m_Receiver_Array-destory();// m_Receiver_Array nullptr;//}}bool execute() override{try{std::optionalT val this-m_Receiver_Array-seek(m_iPos);//判断m_iPos是合法的if (val ! std::nullopt this-m_Receiver_Array-modify(this-m_iPos, m_Val)){printf( Modify Success.);m_Val val.has_value();//用于undo redoreturn true;} printf( Modify Fail.);return false;}catch (...){printf( Modify Fail.);return false;}return true;}virtual bool undo() override{try{if (execute()){printf( Undo Success.);return true;}}catch (...){}printf( Undo Fail.);return false;}virtual bool redo() override{if (execute()){printf( Redo Success.);return true;}printf( Redo Fail.);return false;}
};
template class T
class SeekCommand :public Command
{
private:std::shared_ptrReceiver_ArrayT m_Receiver_Array;
public:SeekCommand():m_bCanRevert(false) {}SeekCommand(std::shared_ptrReceiver_ArrayT _receiver_Array, int _pos) :Command(_pos), m_Receiver_Array(_receiver_Array){m_bCanRevert false;//, m_bCanRevert(false)}virtual ~SeekCommand(){//if (m_Receiver_Array)//{// m_Receiver_Array-destory();// m_Receiver_Array nullptr;//}}bool execute() override{return false;}virtual void* executeOther() override{try{std::optionalT val m_Receiver_Array-seek(m_iPos);if (val std::nullopt){printf( Seek Fail.);return nullptr;}printf( Seek Success.);T* ret new T();*ret val.value();return ret;}catch (...){}printf( Seek Fail.);return nullptr;}virtual bool undo() override{printf( Undo Fail.);return false;}virtual bool redo() override{printf( Redo Fail.);return false;}
};
1Command类是命令基类。本来也想将Command设计成模板类但是后面想想感觉不太好因为Command设计成模板类会影响到CommandMgr也变成模板类。如果Command类是模板类要注意其属性如果在派生类中要用的话要用this指针去访问否则会出现找不到标识符的问题。
可参考
C模板类中派生类使用基类中数据或方法报“找不到标识符”_c头文件引用其他类提示找不到符号-CSDN博客
2Command类中有个m_bCanRevert属性用于判断该命令是否可以被撤销回滚因为并不是所有的命令都支持撤销回滚比如例子中的SeekCommand。
3Command类中有个executeOther因为SeekCommand执行后需要返回一个值是特殊的命令因此executeOther用于执行特殊的命令
4其他的Command派生类依赖于Receiver_Array类可能会出现多个类依赖于同一个Receiver_Array类对象的情况因此把Receiver_Array类成员变量设置为智能指针方便内存的释放
5其他的主要就是实现每个Command类的execute、undo、redo方法这个直接看逻辑就能理解。
3.CommandMgr
//CommandMgr.h
#pragma once
#include stack
#include memory
class Command;
class CommandMgr
{
private:std::stackstd::shared_ptrCommand m_stkUndo;//undo栈std::stackstd::shared_ptrCommand m_stkRedo;//redo栈
public:CommandMgr();~CommandMgr();void execute(std::shared_ptrCommand command) noexcept;void* executeOther(std::shared_ptrCommand command)noexcept;void undo() noexcept;void redo() noexcept;
};
//CommandMgr.cpp
#include CommandMgr.h
#include Command.h
CommandMgr::CommandMgr()
{
}
CommandMgr::~CommandMgr()
{while (!m_stkRedo.empty()){m_stkRedo.pop();}while (!m_stkUndo.empty()){ m_stkUndo.pop();}
}
void CommandMgr::execute(std::shared_ptrCommand command) noexcept
{if (command-execute()){printf( Command Execute Success\n\n);if (command-m_bCanRevert){m_stkUndo.push(command);}}else{printf( Command Execute Fail\n\n);}
}void* CommandMgr::executeOther(std::shared_ptrCommand command) noexcept
{void* val command-executeOther();if (val){printf( Command Execute Success\n\n);if (command-m_bCanRevert){m_stkUndo.push(command);}return val;}else{printf( Command Execute Fail\n\n);}return nullptr;
}void CommandMgr::undo() noexcept
{if (m_stkUndo.empty()){return;}std::shared_ptrCommand command m_stkUndo.top();if (command command-m_bCanRevert command-undo()){ m_stkUndo.pop();m_stkRedo.push(command);printf( Command Undo Success\n\n);}else{printf( Command Undo Fail\n\n);}
}void CommandMgr::redo() noexcept
{if (m_stkRedo.empty()){return;}std::shared_ptrCommand command m_stkRedo.top();if (command command-m_bCanRevert command-redo()){m_stkUndo.push(command);printf( Command Redo Success\n\n);}else{printf( Command Redo Fail\n\n);}
}1CommandMgr主要用于管理命令用来操作具体的命令的调用控制、undo、redo控制。
2因为Command类型对象的内存不太好管理因此也使用了智能指针。
3里面的undo、redo主要通过栈来实现。当命令execute过后便会添加到undo栈接下来的undo、redo主要就是对undo栈和redo栈进行互相倒腾。
4.main函数
当做完上面的工作就能对数组进行方便的增删改查了还可以撤销回退哦。
// LearnCommandProject.cpp : 此文件包含 main 函数。程序执行将在此处开始并结束。#include iostream
#include vector
#include Command.h
#include Receiver_Array.h
#include CommandMgr.h
#include memory
int main()
{std::vectorint vec{ 1,2,3 };std::shared_ptrReceiver_Arrayint receiver_Array(new Receiver_Arrayint(vec));std::shared_ptrAddCommandint addCommand(new AddCommandint(receiver_Array, 3, 4));CommandMgr commandMgr;commandMgr.execute(addCommand);commandMgr.undo();commandMgr.redo();receiver_Array-display();std::shared_ptrSeekCommandint seekCommand(new SeekCommandint(receiver_Array, 1));int* val (int*)(commandMgr.executeOther(seekCommand));receiver_Array-display();delete val;val nullptr;std::shared_ptrDelCommandint delCommand(new DelCommand(receiver_Array, 1));commandMgr.execute(delCommand);commandMgr.undo();commandMgr.redo();receiver_Array-display();std::shared_ptrModifyCommandint modifyCommand(new ModifyCommand(receiver_Array, 2, 2));commandMgr.execute(modifyCommand);commandMgr.undo();commandMgr.redo();receiver_Array-display();printf(ok);
}.上面的代码可能还有设计不好的地方欢迎批评指正。
