copy-constructor

问题 I have the following problem: I have a class which should do this: Obj o; Obj o1(o), o1=o; // deep-copies const Obj c(o), c=o; // deep-copies const Obj c1(c), c1=c; // shallow-copies Obj o2(c), o2=c; // deep-copies How can I do this preferably without inheritance? (I mean I would do Const_obj inheriting from Obj otherwise.) EDIT: Using o.clone() directly is not an option because then I could easily introduce bugs by accidentally not cloning. EDIT: Finally, there is a proper, complete solution

问题 This question already has answers here : Why doesn't Java have a copy constructor? (9 answers) Closed 3 years ago . Does Java has a default copy constructor as C++? If it has one - does it remain usable if I declare another constructor (not a copy constructor) explicitly? 回答1: Java does not have bulit-in copy constructors. But you can write your own such constructors. See an example below: class C{ private String field; private int anotherField; private D d; public C(){} public C(C other){

问题 I'm implementing a templated vector class (not the data container, but the vector in the linear algebra sense), and I'm getting quite a few errors whenever I refer to rhs in my operator overloading. Also, my copy constructor doesn't seem to be working. #ifndef __VecXd__VecXd__ #define __VecXd__VecXd__ #define ULL unsigned long long #include <iostream> using namespace std; template <class T> class VecXd { public: explicit VecXd(ULL newDimension = 1) { dimension = newDimension; vector = new T

问题 This question is regarding bitwise copying of class objects. Why is constructor not called, instead destructor is called in below code ? The output is as HowMany h2 = f(h); // No constructor get;s called here.. after construction of h: objectCount = 1 x argument inside f(): objectCount = 1 ~HowMany(): objectCount = 0 after call to f(): objectCount = 0 ~HowMany(): objectCount = -1 ~HowMany(): objectCount = -2 class HowMany { static int objectCount; public: HowMany() { objectCount++; } static

问题 I have a class with a template constructor, and the code is actually calling the copy constructor, after the default-constructor, which does not make sense to me as the type is incorrect. For example: class A { public: A(void); // default constructor A(const A& other); // copy constructor template<class TYPE> A(const TYPE& object_to_ref); // template constructor }; This template constructor works (is properly called in other cases), but is not properly recognized as the "correct" constructor

问题 I was reading Why would a copy constructor have more than one parameter?. The accepted answer says that: The old std::basic_string does have one too: basic_string(const basic_string& s, size_type pos = 0, size_type n = npos) But http://www.cplusplus.com/reference/string/basic_string/basic_string/ says that: basic_string (const basic_string& str, size_type pos, size_type len = npos, const allocator_type& alloc = allocator_type()); The above isn't a copy constructor but substring constructor

问题 As you know compiler defines default constructor, copy constructor, assignment operator and destructor for POD structures if it weren't defined manually. Usually (or maybe should I say always) it's a bit copy operation. So I've decided to inherit my class from Win structure BITMAP to provide memory allocation in constructor and freeing in destructor. I haven't used composition 'coz I want to allow using it with some WinAPI functions. Here is a some piece of code: class CPreviewFrame : public

问题 Let the example be: class Base { Base (const Base & copyFrom) { globalRegister (* this); } } class Derived { Derived (const Derived & copyFrom) : Base (copyFrom) {} } I've read suggestions to include the Base's copy constructor on the initialisation list of Derived in order to copy over the Base's properties (as in the example). However, I have the Base's copy constructor passing itself (* this) to other object (to be registered with that object). Would that be a case where I actually must

问题 when this copy constructor is called in my application, this copy constructor goes into an infinite loop i.e it keeps calling itself. When i debugged the pogram terminated at the first line itself. The foreach loop used is a Qt foreach. template<class TValue> Locus<TValue>::Locus (const Locus<TValue>& source ) : QVector<TValue>(source) // program terminates here { std::cout << "calling self from here " << std::endl; foreach (typename Locus<TValue>::value_type l, source) { this->push_back(l);

问题 I am struggling with implementing big 3 idea (assignment operator overload, copy constructor, destructor). my code below will crash the program. It compiles so I cannot even see any error hint. Please help. enter code here #include <iostream> using namespace std; #include <string> #include <fstream> #include <cmath> #include <cstdlib> #include <ctime> #include <vector> #include <windows.h> #include <cstring> #include <cctype> #include <iomanip> #include <algorithm> #include<sstream> class