Flyweight

Flyweight

对同样内容的对象，只创建一份。
需要显示对象时，若对象存在，则返回已存在对象的地址；若不存在，则创建对象再返回。

#include  < iostream >
#include  < string >
#include  < list >

using   namespace  std;

// 封装了string
class  Flyweight
{
public:
    Flyweight(string s):str(s){}
    string GetStr(){return str;}
    void Print() const {cout<<str<<endl;}
private:
    string    str;
} ;

// 提供了返回flyweight的接口
class  FlyweightFactory
{
public:
    ~FlyweightFactory()
    {
        list<Flyweight*>::iterator it;
        for(it=lf.begin(); it!=lf.end(); it++)
        {
            delete (*it);
        }
    }

    //若不存在则新建，若存在则返回存在的元素
    const Flyweight* GetFlyweight(const string& s)
    {
        list<Flyweight*>::iterator it;
        for(it=lf.begin(); it!=lf.end(); it++)
        {
            if((*it)->GetStr() == s+"_fly")
            {
                cout<<"exist: ";
                return *it;
            }
        }
        Flyweight *p = new Flyweight(s+"_fly");
        lf.push_back(p);
        cout<<"new: ";
        return p;
    }
private:
    list<Flyweight*> lf;
} ;

int  main()
{
    FlyweightFactory *p = new FlyweightFactory;
    p->GetFlyweight("hello")->Print();
    p->GetFlyweight("hello")->Print();
    p->GetFlyweight("hello")->Print();
    p->GetFlyweight("dog")->Print();
    p->GetFlyweight("dog")->Print();
    p->GetFlyweight("hello")->Print();

    delete p;

    return 0;
}