Lambda expression taking an unique pointer contained in a vector

Question

I have a vector foos of unique pointers to my resource type Foo. I would like to delete some of these that satisfy a given condition. How should I do this ?

class Foo
{
public:
    int some_num;
    Foo(int some_num_) :some_num{ some_num_ }
    {}
    int getNum()
    {
        return some_num;
    }
};

using FooPtr = std::unique_ptr<Foo>;
using Foos = std::vector<FooPtr>;

int main()
{
    Foos foos;
    foos.push_back(std::move(std::make_unique<Foo>(30)));
    foos.push_back(std::move(std::make_unique<Foo>(35)));
    std::vector<int> some_nums = { 35, 30, 25 };
    for each (auto& num in some_nums)
    {
        foos.erase(std::remove_if(foos.begin(), foos.end(), 
             [&](auto foo) {return num == foo->getNum(); }), foos.end());
    }
    return 0;
}

It looks like I'm copying the unique_ptr and so I get the following error,

'std::unique_ptr<Foo,std::default_delete<_Ty>>::unique_ptr(const std::unique_ptr<_Ty,std::default_delete<_Ty>> &)': attempting to reference a deleted function

How should I do this ? I will not be using the resource. I don't care about the ownership beyond this point.

Answer 1

The auto deduction rules will deduce the type to be std::unique_ptr, forcing a copy. So just change the parameter type of the lambda expression to

[&](const auto& foo) {return num == foo->getNum(); })