pass all container elements to member function (for_each and mem_fun_ref)

class Simple
{
};

class Holder
{

     vector<Simple> vec;

     void Do(const Simple& s) const
     {
         // does something with s
     }

     void DoAll()
     {
         for_each(vec.begin(), vec.end(), mem_fun_ref(&Holder::Do));
     }

};

Here is what I get: term does not evaluate to a function taking 1
arguments

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