因此,我对C ++及其附带的所有内存管理还很陌生。
我的问题是我在扩展函数中创建一个对象,然后将该对象分配给同一类的另一个对象中的成员变量(该类是一个二进制树,其数据是InVec对象)。
函数运行后,给定SPnode的m_left和m_right的内存位置相同,但是取消引用的值是垃圾。
我几乎可以肯定,这是由于InVec和SPnode对象超出范围并被破坏了,因此产生了指向垃圾的指针m_left和m_right。
我的问题是:如何在函数内部创建对象,将其分配给成员变量,并且在函数终止时如何销毁它?我确定我遗漏了一些明显的东西,但是我一直无法在任何地方找到答案(我什至不知道该如何措辞)。
这是我的代码:
void expand(SPnode &ASP)
{
if (!(ASP.isLeaf())) return;
int axis(ASP.m_box.getWidthAxis());
Interval width(ASP.m_box.getWidth());
InVec lowerInVec(lower(ASP.m_box, width, axis));
InVec upperInVec(upper(ASP.m_box, width, axis));
SPnode leftChild(lowerInVec);
std::cout << &leftChild << "\n";
SPnode rightChild(upperInVec);
std::cout << &rightChild << "\n";
ASP.m_left = &leftChild;
std::cout << (ASP.m_left) << "\n";
ASP.m_right = &rightChild;
std::cout << (ASP.m_right) << "\n";
}
如果此代码格式不正确或违反了一些重要规则,我深表歉意。任何建设性的批评也将不胜感激。
编辑:这是间隔,InVec和SPnode的相关代码:
// The Interval class is the base object on which all other classes in this
// module are built. Its implementation is intuitive, as all mathematical
// operations that are relevant for nonlinear image computation are given
// as overloaded operators (i.e. intervalA + intervalB returns the expected
// result from basic interval arithmetic).
class Interval
{
private:
// infimum (lower bound) of interval
double m_inf;
//supremum (upper bound) of interval
double m_sup;
public:
Interval(double inf, double sup): m_inf(inf), m_sup(sup) {}
// getter member functions, where getLen returns the length of the interval
// and getMidpt returns the midpoint
double getInf() const {return m_inf;}
double getSup() const {return m_sup;}
double getLen() const {return m_sup - m_inf;}
double getMidpt() const {return (m_inf + m_sup)/2.0;}
// --- Headers -----------------------------------------------------------------
// determines if a double is in the interval
bool containsVal(double val) const;
// determines if another interval is contained in the interval
bool contains(const Interval &other) const;
// performs scalar multiplication on the interval
Interval scalarMul(double scal) const;
// operator overloading - the specifics of interval arithmetic can be found
// in a book or online
friend Interval operator+(const Interval &intA, const Interval &intB);
friend Interval operator-(const Interval &intA, const Interval &intB);
friend Interval operator*(const Interval &intA, const Interval &intB);
friend bool operator==(const Interval &intA, const Interval &intB);
friend bool operator!=(const Interval &intA, const Interval &intB);
friend std::ostream& operator<< (std::ostream &out, const Interval &intA);
friend void expand(SPnode &ASP);
friend InVec lower(const InVec &box, const Interval &width, int axis);
friend InVec upper(const InVec &box, const Interval &width, int axis);
};
class InVec
{
private:
// this is a vector containing the Interval objects that make up the InVec
// object
std::vector<Interval> m_intervals;
public:
InVec(std::vector<Interval> intervals): m_intervals(intervals) {}
// returns m_intervals
std::vector<Interval> getIntervals() const {return m_intervals;}
// returns the interval at given axis (i.e. index) in m_intervals
Interval getInterval(int axis) const {return m_intervals.at(axis);}
// sets the interval at given axis to given Interval object
void setInterval(int axis, const Interval &intA)
{m_intervals.at(axis) = intA;}
// --- Headers -----------------------------------------------------------------
// determines if another InVec object is contained in this InVec object
bool contains(const InVec &IVB) const;
// returns the length of the largest Interval object in m_intervals - note
// that it is necessary to compute this first, before the actual largest
// Interval can be determined
double getWidthSize() const;
// returns the Interval in m_intervals with the longest length
// (i.e. the width)
Interval getWidth() const;
// returns the axis (i.e. index) on which the width occurs
double getWidthAxis() const;
// operator overloading
friend InVec operator+(const InVec &IVA, const InVec &IVB);
friend InVec operator-(const InVec &IVA, const InVec &IVB);
friend InVec operator*(const InVec &IVA, const InVec &IVB);
friend bool operator==(const InVec &intA, const InVec &intB);
friend bool operator!=(const InVec &intA, const InVec &intB);
friend std::ostream& operator<< (std::ostream &out, const InVec &IVA);
friend void expand(SPnode &ASP);
friend InVec lower(const InVec &box, const Interval &width, int axis);
friend InVec upper(const InVec &box, const Interval &width, int axis);
};
class SPnode
{
private:
InVec m_box;
// left and right children of this SPnode object - note that these must be
// pointers in order to use them in the definition of the class, otherwise
// SPnode would have an inifinite definition
SPnode* m_left;
SPnode* m_right;
public:
SPnode(InVec box): m_box(box), m_left(NULL), m_right(NULL) {}
// getters and setters
InVec getBox() const {return m_box;}
SPnode* getLeft() const {return m_left;}
SPnode* getRight() const {return m_right;}
void setBox(const InVec box) {m_box = box;}
void setLeft(SPnode* const p_node) {m_left = p_node;}
void setRight(SPnode* const p_node) {m_right = p_node;}
bool isLeaf() const;
friend std::ostream& operator<< (std::ostream &out, const SPnode &ASP);
friend void expand(SPnode &ASP);
friend InVec lower(const InVec &box, const Interval &width, int axis);
friend InVec upper(const InVec &box, const Interval &width, int axis);
};
您应该将子代创建为指针,并使用new运算符动态分配它们,如下所示:
SPnode * leftChild = new SPnode(lowerInVec);
然后将其分配给对象成员变量,如下所示:
ASP.m_left = leftChild;
同样,您应该将m_left声明为SPnode指针,如下所示:
SPNode * m_left;
对右边的人做同样的事情。
附注:在理解智能指针之前,您应该了解使用new运算符分配的指针。
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