C++指针问题

我很抱歉,因为这是一个不太好的问题,但我想不出这一个。

class View //simplified
{
public:
  ROILine* ROI() {return _roi;} //setter does some control stuff...
private:
  ROILine *_roi;
}

class ROI : public eq::Object
{

public:
    //virtual ROI(ROI* copy) = 0;
    virtual ~ROI() {};

    virtual uint32_t getType() = 0;

    virtual void reset() = 0;

    virtual bool addPoint( eq::Vector3f point ) = 0;
    virtual bool previewPoint( eq::Vector3f point ) = 0;

    virtual bool getNotationLocation( eq::Vector3f& point ) = 0;

    virtual bool draw() = 0;

protected:

    enum ROIType {
        NONE = 0,
        LINE,
        POLY,
        AREA,
        VOLUME
    };

    enum ROIMeasure {
        RM_LENGTH = 1,
        RM_AREA,
        RM_VOLUME,
    };

private:

};


class ROILine : virtual public ROI
{

public:
    ROILine();
    ROILine(ROILine* copy);
    ROILine(const ROILine& copy);
    virtual ~ROILine() {SFLog(@"Destroying ROILine: 0x%x",this);};
    void reset();

    float distance() { return _start.distance(_end); }


    // ROI Interface
    uint32_t getType() { return ROI::LINE; }
    virtual bool draw();
    bool addPoint( eq::Vector3f point );
    bool previewPoint( eq::Vector3f point );
    bool getNotationLocation( eq::Vector3f& point );

    eq::net::DataOStream& serialize(eq::net::DataOStream& os) ;
    eq::net::DataIStream& deserialize(eq::net::DataIStream& is) ;

protected:

    enum ROILineState { // RLS_
        RLS_RESET,
        RLS_START,
        RLS_PREVIEW,
        RLS_END,
    };

private:
    uint32_t _state;
    eq::Vector3f _start;
    eq::Vector3f _end;
};

ROILine::ROILine(const ROILine& copy) : ROI()
{
    reset();
    switch (copy._state) 
    {
        case RLS_PREVIEW:
        case RLS_END:
            addPoint(eq::Vector3f(copy._start));
            addPoint(eq::Vector3f(copy._end));
            break;
        case RLS_START:
            addPoint(eq::Vector3f(copy._start));
            break;
        case RLS_RESET:
        default:
            break;
    }
}

/*!
 @abstract resets the line values and state
 */
void ROILine::reset()
{
    _state = RLS_RESET;
    _end = eq::Vector3f::ZERO;
    _start = eq::Vector3f::ZERO;
}
/*!
 @abstract if it has 2 points, draw the line. (_state > _PREVIEW)
 @discussion assumes GL is already set up.  Executes drawing commands.
 @result true if the line was drawn
 */
bool ROILine::draw()
{
    bool retVal = false;

    if (_state >= RLS_PREVIEW) {
        //glTranslatef(0.0f, 0.0f, -1.0f); //Back Up?
        glColor3f( 1.0f, 0.0f, 0.0f );  //Red
        glEnable( GL_LINE_SMOOTH );
        glLineWidth( 1 );
        glBegin( GL_LINES );
        {
            glVertex3fv( _start.array );
            glVertex3fv( _end.array );
        }
        glEnd();    
        //glTranslatef(0.0f, 0.0f, 1.0f); // Return
        retVal =  true;
    } 

    return retVal;

}

// Elsewhere...

View *v = getView(); // returns the view object

// Destroys each time, but works wonderfully
ROILine r = ROILine(*(v->ROI()));
r.draw();

// Does not work (EXC_BAD_ACCESS)
v->ROI()->draw();

// Does not work (EXC_BAD_ACCESS on draw());
ROILine *r = v->ROI();
r->draw(); // debug shows r != 0x0

我遇到的错误如下 r->draw() 然后继续。

[Switching to process 12453]
Current language:  auto; currently objective-c++
Warning: the current language does not match this frame.
(gdb) continue 
Program received signal:  “EXC_BAD_ACCESS”.

这个 "EXC_BAD_ACCESS" 发生于 R->绘制() 或 v->ROI()->draw() 它根本就没有进入程序,只是停下来 bt 给我一个 ??

我的复制构造函数可以工作,因为draw()函数实际上在它应该绘制的位置(而不是!啊!4!#@土地)我不理解的是,为什么复制价值是有效的,但是访问 v->ROI()->绘制()) 没有。它 必须 有 v->ROI() 为了复制!!

对?…不?

如此困惑…

谢谢,