the leak of the memory in c++ 03

The Leak of the Memory in C++

In this chaper I will introduce a new smart pointer which is scoped_ptr;

It likes auto_ptr but better. When peopel use auto_ptr, sometimes they forget

that auto_ptr alread is empty, like this;

 auto_ptr<Person> p1(new Person);
    auto_ptr<Person> p2 = p1;
    cout << p1->name() << endl;

In above situation, p1 is empty pointer after it gives pointee to p2. It

will produce some error.

But scoped_ptr can‘t give pointee to any pointer, so it will be better and

safer in some cases.

Now I‘ll introduce some special pattern to you, I say special, because in

normal cases, it just used in C++; In articles which I wrote before, I avoided

to use operator of delete, but I still use new operator, in this article I‘ll

introduce method which can help us to avoid use new operator.

Now let us welcome our pattern: PIMPL, it means Pointer to Implement. It

looks like below.

PersonImpl.h

class PersonImpl
{
public:
    PersonImpl()
    {
        cout << "I'm constructed" << endl;
    }
    ~PersonImpl()
    {
        cout << "I'm destructed!" << endl;
    }

private:
    int age_;
    string name_;
public:
    const string& getName()const
    {
        return name_;
    }
    void setName(const string& name)
    {
        name_ = name;
    }

    int getAge()
    {
        return age_;
    }

    void setAge(int age)
    {
        age_ = age;
    }
};

Person.h

using namespace std;
using namespace boost;

class Person
{

public:
    Person() :
        personPtr_(new PersonImpl)
    {}

    ~Person()
    {
    };
private:
    scoped_ptr<PersonImpl> personPtr_;

public:
    int getAge()
    {
        return personPtr_->getAge();
    }

    void setAge(int age)
    {
        personPtr_->setAge(age);
    }

    const string& getName()const
    {
        return personPtr_->getName();
    }

    void setName(const string& name)
    {
        personPtr_->setName(name);
    }
};

main.cpp

using namespace std;
using namespace boost;

int main(int,char**)
{
    Person person;
    return 0;
}

In above code, I did not implement Person directly, instead of a smart

pointer which point a class which implement Person. So we can use class Person

just like I use it in main function without new neither delete operators.

the leak of the memory in c++ 03