Yes. There are two common options. One – which is generally discouraged – is to call the operator= from the copy constructor explicitly: MyClass(const MyClass& other) { operator=(other); } However, providing a good operator= is a challenge when it comes to dealing with the old state and issues arising from self assignment. Also, all members … Read more
The copy constructor generated by the compiler does member-wise copying. Sometimes that is not sufficient. For example: class Class { public: Class( const char* str ); ~Class(); private: char* stored; }; Class::Class( const char* str ) { stored = new char[srtlen( str ) + 1 ]; strcpy( stored, str ); } Class::~Class() { delete[] stored; … Read more
Because if it’s not by reference, it’s by value. To do that you make a copy, and to do that you call the copy constructor. But to do that, we need to make a new value, so we call the copy constructor, and so on… (You would have infinite recursion because “to make a copy, … Read more
Clone is broken, so dont use it. THE CLONE METHOD of the Object class is a somewhat magical method that does what no pure Java method could ever do: It produces an identical copy of its object. It has been present in the primordial Object superclass since the Beta-release days of the Java compiler*; and … Read more
In the following, “auto-generated” means “implicitly declared as defaulted, but not defined as deleted”. There are situations where the special member functions are declared, but defined as deleted. The default constructor is auto-generated if there is no user-declared constructor (ยง12.1/5). The copy constructor is auto-generated if there is no user-declared move constructor or move assignment … Read more
You can make the copy constructor private and provide no implementation: private: SymbolIndexer(const SymbolIndexer&); Or in C++11, explicitly forbid it: SymbolIndexer(const SymbolIndexer&) = delete;
Overview Why do we need the copy-and-swap idiom? Any class that manages a resource (a wrapper, like a smart pointer) needs to implement The Big Three. While the goals and implementation of the copy-constructor and destructor are straightforward, the copy-assignment operator is arguably the most nuanced and difficult. How should it be done? What pitfalls … Read more
Introduction C++ treats variables of user-defined types with value semantics. This means that objects are implicitly copied in various contexts, and we should understand what “copying an object” actually means. Let us consider a simple example: class person { std::string name; int age; public: person(const std::string& name, int age) : name(name), age(age) { } }; … Read more