Trying to disable a function if any type of list is passed in
c++, sfinae, template-meta-programming
Solution
The direct problem is here:
std::list<typename ContainerType::value_type>>::value>>
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In your example, `ContainerType` is a reference type (`std::vector<int>&`) and you can't access typedefs off of a reference type. You'd have to remove the reference first.
But we can do it simpler by just ignoring the `KeyType` part:
template <class X> struct is_list : std::false_type { };
template <class T, class A> struct is_list<std::list<T,A>> : std::true_type { };
template <class Container, class Key,
std::enable_if_t<!is_list<std::decay_t<Container>>::value>* = nullptr>
void func(ContainerType&&, Key&& ) { ... }
Problem
I am trying to disable a function if any type of a list class is passed into the function with the following enable_if ``` template <typename ContainerType, typename KeyType, typename = std::enable_if_t<!std::is_same< std::decay_t<ContainerType>, std::list<typename ContainerType::value_type>>::value>> void func(ContainerType&& container, KeyType&& key) ``` But when I call func with `vector<int>` I get the error ``` candidate template ignored: substitution failure [with ContainerType = std::__1::vector<int, std::__1::allocator<int> > &, KeyType = int]: type 'std::__1::vector<int, std::__1::allocator<int> > &' cannot be used prior to '::' because it has no members ``` A vector does have the member typedef `value_type` to get the value of the thing stored in it.. Any idea how I can go about fixing this?