如何在C ++中初始化类中的非静态const变量？

Question

I wrote these following codes in Stack.h:

class Stack{
public:
    inline bool full();
    int size();
    inline bool empty();
    bool push(const string&);
    bool pop(string &s);
    bool peek(string &s);
    virtual void print();
    virtual ~Stack(){}

protected:
    vector<string> _elem;
    int const _maxsize=10;    // line X
};

I got the error:

Stack.h:14: error: ISO C++ forbids initialization of member ‘_maxsize’
Stack.h:14: error: making ‘_maxsize’ static
make: *** [Stack.o] Error 1

if I add a static keyword at line X, and initialize the variable outside the class definition, it could be OK.

But my question is that is there any possible way to declare a non-static const variable and still successfully initialize it???

Answer 1

Yes, initialize this in your constructor

const int NumItems;

Foo::Foo():
NumItems(15)
{
//....
}

Answer 2

This is valid in C++11. In C++03 you'll have to initialize it in the constructor. Alternitively, in C++11:

class Stack{
    int const _maxsize{10};
};

Answer 3

You can use enum

class C {
  protected:
    enum { var = 10 }; 
}

In this case C::var will be compile-time constant, that can be even used in a template.

Also, c++11 allows the declaration you're trying to use.