设计模式（一）Singleton,Command

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//: C10:SingletonPattern.cpp

#include <iostream>

using namespace std;

class Singleton {

  static Singleton s;

  int i;

  Singleton(int x) : i(x) { }

  Singleton& operator=(Singleton&);  // Disallowed

  Singleton(const Singleton&);       // Disallowed

public:

  static Singleton& instance() { return s; }

  int getValue() { return i; }

  void setValue(int x) { i = x; }

};

Singleton Singleton::s(47);

int main() {

  Singleton& s = Singleton::instance();

  cout << s.getValue() << endl;

  Singleton& s2 = Singleton::instance();

  s2.setValue(9);

  cout << s.getValue() << endl;

} ///:~

Command:

可以说，命令模式是携带行为信息的信使。

//: C10:CommandPattern.cpp

#include <iostream>

#include <vector>

using namespace std;

class Command {

public:

    virtual void execute() = 0;

};

class Hello : public Command {

public:

    void execute() { cout << "Hello "; }

};

class World : public Command {

public:

    void execute() { cout << "World! "; }

};

class IAm : public Command {

public:

    void execute() { cout << "I'm the command pattern!"; }

};

// An object that holds commands:

class Macro {

    vector<Command*> commands;

public:

    void add(Command* c) { commands.push_back(c); }

    void run() {

        vector<Command*>::iterator it = commands.begin();

        while(it != commands.end())

            (*it++)->execute();

};

int main() {

    Macro macro;

    macro.add(new Hello);

    macro.add(new World);

    macro.add(new IAm);

    macro.run();

} ///:~

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