如何从向量中删除元素<shared_ptr>

Question

I´m buiding a sort of a registry class using the following code:

class MyClass 
{
    public:
       int a;
       std::string b;
};

class Register
{
    public:
        std::vector<std::shared_ptr<MyClass>> items;

        bool registerItem(std::shared_ptr<MyClass> item)
        {
            /*
             * Check if item exists
             */
            auto position = std::find(items.begin(), items.end(), item);

            if (position != items.end())
                return false;

            items.push_back(item);

            return true;
        }

         bool unregisterItem(std::shared_ptr<MyClass> item)
        {
            auto position = std::find(items.begin(), items.end(), item);

            if (position == items.end())
               return false;

            items.erase(item);

            return true;
        }
};


int main()
{
    std::shared_ptr<MyClass> item1 = new MyClass;

    Register registry;

    if (!registry.registerItem(item1))
        std::cout << "Error registering item1" << std::endl;
    else
        std::cout << "Success registering item1" << std::endl;

    if (!registry.registerItem(item1))
        std::cout << "Error unregistering item1" << std::endl;
    else
        std::cout << "Success unregistering item1" << std::endl;
}

I can´t compile this code, as items.erase(item) complains about error: no matching member function for call to 'erase' .

Why I can´t erase the object I´ve added. What is the correct way to remove a std::shared_ptr from a std::vector ?

Answer 1

因为要在items使用迭代器（ 即 position ），所以：

items.erase(position);

Answer 2

There are two declarations available. From cppreference :

iterator erase (const_iterator position);
iterator erase (const_iterator first, const_iterator last);

You try to std::vector::erase the item itsself instead of the iterator. Use

items.erase(position);

instead.

Answer 3

You have to call erase on position , not item
since erase is used on iterators

Answer 4

You should pass to erase iterator not a value, there is nothing special with deleting std::shared_ptr. Also you have mistype in code: you register item twice instead of unregister it in the second call.