scope_ptr

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

template <typename T>
class scoped_ptr
{
public:
    typedef T elememnt_type;
    explicit scoped_ptr(T* p = 0) :px(p){ cout << "scoped_ptr construct" << endl; };
    ~scoped_ptr(){ cout << "scoped_ptr deconstruct" << endl; delete px; }
    T& operator*()const
    {
        assert(px != 0);
        return *px;
    }
    T* operator->()const
    {
        assert(px != 0);
        return px;
    }
    T* get()const
    {
        return px;
    }
    void swap(scoped_ptr& p)
    {
        T* temp = p.px;
        p.px = px;
        px = temp;
    }
    void reset(T* p = 0){
        assert(p == 0 || p != px);
        scoped_ptr<T>(p).swap(*this);//这句话很吊
        //用临时对象交换指针，把p给了this对象，临时对象消亡delete this；
    }
    operator bool()
    {
        cout << "scoped_ptr operator bool()" << endl;
        return px != 0;
    }
    bool operator!()
    {
        cout << "scoped_ptr bool operator!()" << endl;
        return px == 0;
    }
private:
    T* px;
    scoped_ptr(const scoped_ptr& ptr);
    scoped_ptr& operator=(const scoped_ptr& ptr);
    bool operator==(const scoped_ptr& ptr);
    bool operator!=(const scoped_ptr& ptr);
};

int main(){
    scoped_ptr<int> p(new int(10));//scoped_ptr construct
    if (p)
    {
        cout << "p true" << endl;//p true
    }
    else
    {
        cout << "p false"<<endl;
    }
    scoped_ptr<int> p2(new int(20));
    p2.swap(p);
    cout << *p << ends << *p2 << endl;//20 10
    p2.reset(new int(100));//scoped_ptr construct scoped_ptr deconstruct 
    cout << *p << ends << *p2 << endl;//20 100
    return 0;
}