//编的一个简单的通讯录的类 对静态成员的运用编译总是报错
class AddressBook
{
public:
    AddressBook(string aName = "NULL",int aPhonenum = 0);
    ~AddressBook();
    static int getLength();
    static void addLength();
    static void decLength();
    void setName(string aName);
    string getName();
    void setPhonenum(int aPhonenum);
    int getPhonenum();
private:
    string m_strName;
    int    m_iPhonenum;
    static int m_s_ilength;
};
AddressBook::AddressBook(string aName /* = "NULL" */,int aPhonenum /* = 0 */)
{
    m_strName = aName;
    m_iPhonenum = aPhonenum;
}
AddressBook::~AddressBook()
{
    --m_s_ilength;
}

错误是AddressBook.obj : error LNK2001: 无法解析的外部符号 "private: static int AddressBook::m_s_ilength" (?m_s_ilength@AddressBook@@0HA)
求解

后边那个析构函数有错吗？我删了它就不报错了，不知道为什么