Structural Patterns - Flyweight

Flyweight1.cpp

// Flyweight.h
#include <string>
#include <map>
#include <vector>
#include <iostream>
using namespace std;

class AbstractFont      // Flyweight抽象类
{
protected:
    string font_name;      // IntrinsicState，即内部状态

public:
    virtual void set_font_name(string font_name) = 0;    // operation
    virtual string get_font_name() = 0;                               
    virtual string display() = 0;
public:
    virtual ~AbstractFont()
    {
        cout << "in the destructor of AbstractFont..." << endl;
    }
};

class SongTiFont : public AbstractFont      // ConcreteFlyweight
{
public:
    SongTiFont(string font_name)
    {
        this->font_name = font_name;
    }

    string display()
    {
        return font_name;
    }

    string get_font_name()
    {
        return font_name;
    }

    void set_font_name(string font_name)
    {
        this->font_name = font_name;
    }

public:
    ~SongTiFont()
    {
        cout << "in the destructor of SongTiFont..." << endl;
    }
};

class FontFactory      // FlyweightFactory
{
private:
    map<string, AbstractFont*> fonts;      // 这就是pool of flyweights

public:
    AbstractFont* get_font(string font_name)      // GetFlyweight，font_name就是key
    {
        AbstractFont *font;
        // 根据key font_name查找对应的Flyweight
        map<string, AbstractFont*>::iterator it = fonts.find(font_name);

        if(it == fonts.end())      // 如果要找的Flyweight不存在
        {
            font = new SongTiFont(font_name);       // 创建一个新的Flyweight
            fonts.insert(pair<string, AbstractFont*>(font_name, font));       // 加入到pool of flyweights
        }
        else // 如果要找的Flyweight已经存在
        {
            font = it->second;
        }

        return font; // 返回Flyweight
    }

    size_t get_number()
    {
        return fonts.size();
    }

public:
    ~FontFactory()
    {
        cout << "in the destructor of FontFactory..." << endl;
        for(map<string, AbstractFont*>::iterator iter = fonts.begin(); iter != fonts.end(); )
        {
            delete iter->second;      // 在STL中，如果容器中装载的是指针而非值对象，则内存回收
            iter = fonts.erase(iter);       // 的工作，要程序员自己完成。
            //iter--;
        }
    }
};

class FontedCharacter      // 这是一个应用类
{
private:
    string character;
    AbstractFont *font;

public:
    FontedCharacter()    // 之所以要有缺省构造函数，因为Flyweight.cpp中，FontedCharacter chars[10];
    {                                                                        
    }

    FontedCharacter(string character, AbstractFont *font)
    {
        this->character = character;
        this->font = font;
    }

    string set_font()
    {
        return character + " - " + font->display();
    }

public:
    ~FontedCharacter()
    {
        cout << "in the destructor of FontedCharacter..." << endl;
    }
};

// Flyweight.cpp
//#include "Flyweight.h"

int main(int argc, char **argv)
{
    FontFactory *ff = new FontFactory();

    FontedCharacter chars[10];

    chars[0] = FontedCharacter("A", ff->get_font("宋体红色"));      // 1
    chars[1] = FontedCharacter("B", ff->get_font("宋体红色"));     // 2
    chars[2] = FontedCharacter("C", ff->get_font("宋体红色"));     // 3
    chars[3] = FontedCharacter("D", ff->get_font("宋体红色"));     // 4
    chars[4] = FontedCharacter("E", ff->get_font("宋体红色"));      // 5
    chars[5] = FontedCharacter("F", ff->get_font("宋体黑色"));       // 6
    chars[6] = FontedCharacter("G", ff->get_font("宋体黑色"));       // 7
    chars[7] = FontedCharacter("H", ff->get_font("宋体黑色"));       // 8
    chars[8] = FontedCharacter("I", ff->get_font("宋体黑色"));         // 9
    chars[9] = FontedCharacter("J", ff->get_font("宋体黑色"));        // 10

    cout << endl;
    for(int i = 0; i < 10; i++)
    {
        cout << chars[i].set_font() << endl;
    }

    cout << "\n实际有" << ff->get_number() << " 种字体" <<endl;

    delete ff;

    return 0;
}