Item 9: Prefer Alias Declarations to typedefs
Because alias declarations may be templatized but typedefs can’t.
template<typename T>
using MyAllocList = std::list<T, MyAlloc<T>>;
MyAllocList<Foo> lw;
template<typename T>
class Foo {
MyAllocList<T> list;
};
The equivalent code with typedef is:
template<typename T>
struct MyAllocList {
typedef std::list<T, MyAlloc<T>> type;
};
MyAllocList<Foo>::type lw;
template<typename T>
class Foo {
typename MyAllocList<T>::type list;
};
In C++14, type traits are migrated to alias declarations:
#include <type_traits>
std::remove_const<T>::type // C++11
std::remove_const_t<T> // C++14
