c ++私有属性可以在构造函数中使用,但在其他方法中可以使用seg错误

Question

我正在调试一些代码,这让我很健康.

这是一个单例类,它在getInstance方法中为此行提供了seg错误

cerr << _magazineList->_magazines.size() << endl;

我在构造函数中做了同样的事情.

MagazineList* MagazineList::_magazineList = NULL;

MagazineList::MagazineList()
{
        //Initialize the vector of magazines
        _magazines.push_back(Magazine("1", "Design Times", 20.0));
        _magazines.push_back(Magazine("2", "UML News", 50.0));
        cerr << this->_magazines.size() << endl;
};

MagazineList* MagazineList::getInstance()
{
        if ( _magazineList == NULL ) {
                _magazineList == new MagazineList;
                cerr << "getInstance constructing" << endl;
                cerr << _magazineList->_magazines.size() << endl;
        }

                cerr << "getInstance returning" << endl;
        return _magazineList;
};

MagazineList::~MagazineList()
{
        //Delete magazines in magazines vector
};

...

.h文件

using std::vector;

class MagazineList
{
        private:
                int _numberOfMagazines;
                vector<Magazine> _magazines;

                static MagazineList* _magazineList;
                MagazineList();
        public:
                static MagazineList* getInstance();
                ~MagazineList();

                int getNumberOfMagazines();
                void setNumberOfMagazines(int number);
                Magazine* getMagazine(string magId);

                void newMagazine();
                void removeMagazine();
};

Answer 1

这一行:

_magazineList == new MagazineList;

应该:

_magazineList = new MagazineList;