设计模式之命令模式

1,命令(command)模式最大的特点:允许向一个函数或者对象传递一个想要的动作.

#include <iostream>
#include <vector>
using namespace std;

class Command
{
public:
    //接口,执行的动作
    virtual void execute()=0;
};

class Hello:public Command
{
public:
    void execute(){ cout<<"Hello!"<<endl; }
};

class Word:public Command
{
public:
    void execute(){ cout<<"Word!"<<endl; }
};

class Pattern:public Command
{
public:
    void execute(){ cout<<"Command Pattern!"<<endl; }
};

class TaskRun
{
    vector<Command*> commands;
public:
    //添加命令动作.
    void add(Command* e){ commands.push_back(e); }
    //执行
    void run()
    {
        vector<Command*>::iterator ite=commands.begin();
        while(ite!=commands.end())
            (*ite++)->execute();
    }
};

int main()
{
    TaskRun comptn;
    comptn.add(new Hello);
    comptn.add(new Word);
    comptn.add(new Pattern);
    comptn.run();
    return 0;
}

2,一个稍微复杂的程序

#include <iostream>
#include <vector>
#include <ctime>
#include <string>
#include <cstdlib>
using namespace std;

class Command
{
public:
    //接口,执行的动作
    virtual void execute()=0;
};
class CommandRunner
{
    //设置为单件
    static vector<Command*> commands;
    CommandRunner(){}
    CommandRunner(const CommandRunner&);
    CommandRunner& operator=(CommandRunner&);
    static CommandRunner cr;
public:
    //添加命令动作.
    static void add(Command* e){ commands.push_back(e); }
    //执行
    static void run()
    {
        vector<Command*>::iterator ite=commands.begin();
        while(ite!=commands.end())
            (*ite++)->execute();
    }
};
CommandRunner CommandRunner::cr;
vector<Command*> CommandRunner::commands;
//Command和Runner是一个固定的框架

//事件驱动类
class EventSimulator
{
    clock_t creation;
    clock_t delay;
public:
    EventSimulator():creation(clock())
    {
        delay=CLOCKS_PER_SEC/4*(rand()%20+1);
        cout<<"delay= "<<delay<<endl;
    }
    bool fired()
    {
        return clock()>creation+delay;
    }
};

//事件驱动按钮
class Button
{
    bool pressed;
    string id;
    EventSimulator e;
public:
    Button(string name) : pressed(false), id(name) {}
    void press(){ pressed=true; }
    bool isPressed()
    {
        if(e.fired()) press();
        return pressed;
    }
    friend ostream& operator<<(ostream& os,const Button& b)
    {
        return os<<b.id;
    }
};

//执行按钮
class CheckButton:public Command
{
    Button& button;
    bool handled;
public:
    CheckButton(Button& b) : button(b),handled(false){}
    void handle(){ handled=true; }
    void execute()
    {
        if(button.isPressed()&&!handled)
        {
            cout<<button<<" pressed"<<endl;
            handle();
        }
    }
};


int main()
{
    srand(time(0));
    Button b1("Button1");
    Button b2("Button2");
    Button b3("Button3");
    CheckButton cb1(b1),cb2(b2),cb3(b3);
    CommandRunner::add(&cb1);
    CommandRunner::add(&cb2);
    CommandRunner::add(&cb3);
    while(true)
        CommandRunner::run();
    return 0;
}