11.22

#include <iostream>

#include <stack>

#include <string>

using namespace std;

 

class Command

{

public:

    Command(){}

    virtual ~Command(){}

 

    virtual void Execute() = 0;

};

 

 

class InputCommand : public Command

{

    public:

 

        InputCommand( const std::string &input )

        {

            mInput = input;

        }

        ~InputCommand()

        {}

 

        void Execute()

        {

            printf( "当前字符串: %s\n", mInput.c_str() );

        }

 

private:

 

    std::string mInput;

};

 

class Commander

{

public:

    Commander( Command *pCmd )

    {

        //最初的命令数据

        mUndo.push( pCmd );

    }

    ~Commander()

    {

        while( false == mUndo.empty() )

        {

            delete mUndo.top();

            mUndo.pop();

        }

        while( false == mRedo.empty() )

        {

            delete mRedo.top();

            mRedo.pop();

        }

    }

 

    void ExecuteCommand( Command *pCmd )

    {

        pCmd->Execute();

        mUndo.push( pCmd );

    }

 

    void Undo()

    {

        if( mUndo.size() < 2 )

        {

            //无法后退撤销没有数据

            printf( "撤销失败.\n" );

            return;

        }

 

        printf( "撤销:\n" );

 

        //当前命令

        auto pCmd = mUndo.top();

 

        //保存当前命令

        mRedo.push( pCmd );

 

        //弹出

        mUndo.pop();

 

        //还原到上个命令

        pCmd = mUndo.top();

 

        pCmd->Execute();

    }

 

    void Redo()

    {

        if( mRedo.empty() )

        {

            //无法前进重做没有数据

            printf( "重写失败.\n" );

            return;

        }

 

        printf( "重写:\n" );

 

        auto pCmd = mRedo.top();

 

        pCmd->Execute();

 

        mRedo.pop();

 

        mUndo.push( pCmd );

    }

 

private:

    std::stack< Command* > mUndo;

    std::stack< Command* > mRedo;

};

 

int main()

{

    //默认没有输入字符串可以是空，这里为了演示赋值一个特殊的字符串

    Commander *p = new Commander( new InputCommand( "[empty]" ) );

 

    //输入1234

    p->ExecuteCommand( new InputCommand( "123" ) );

    //输入567

    p->ExecuteCommand( new InputCommand( "567" ) );

    //输入xxx

    p->ExecuteCommand( new InputCommand( "xxx" ) );

 

    //执行一次undo 撤销到 567

    p->Undo();

    //执行一次undo 撤销到 1234

    p->Undo();

 

    //undo后中间输入新字符串 insert 覆盖 1234

    p->ExecuteCommand( new InputCommand( "insert" ) );

 

    //执行一次undo 撤销到 1234

    p->Undo();

 

    //执行一次undo 撤销到最初情况 [empty]

    p->Undo();

 

    //执行失败已经undo 到最原始情况

    p->Undo();

 

    //执行一次redo 重做到 1234

    p->Redo();

    //执行一次redo 重做到 insert

    p->Redo();

    //执行一次redo 重做到 567

    p->Redo();

 

    //redo后中间输入新字符串 insert again 覆盖 567

    p->ExecuteCommand( new InputCommand( "insert again" ) );

 

    //执行一次undo 撤销到567

    p->Undo();

 

    //执行一次redo 重做到 insert again

    p->Redo();

 

    //执行一次redo 重做到 xxx

    p->Redo();

 

    //执行失败已经redo 到最新情况

    p->Redo();

    delete p;

    return 0;

}