// copy-and-swap示例 struct Foo{ // 实现方式一:不检查self-assignment // // 由于自赋值的情况极其罕见,并无必要做自赋值检查 Foo& operator=(const Foo& s) { Foo temp(s); // 调用Copy-constructor -- RAII temp.swap(*this); // Non-throwing swap return *this; }// Old resources released...
理解并正确实现拷贝赋值运算符是编写高效、安全C++代码的关键，这涉及到函数声明、调用场景以及潜在的自定义需求。通过遵循最佳实践和相关规范，可以确保代码的稳定性和可读性。对于更深入的探讨，可以参考[1] Copy assignment operator的详细文档。
1. 如果要在内含reference成员的class内支持赋值操作,编译器拒绝生成copy assignment,必须自己定义copy assignment操作符; 2. 如果要在内含const成员的class内支持赋值操作,更改const成员不合法,编译器拒绝生成copy assignment; 3. 如果base class将copy assignment操作符声明为private,编译器拒绝为其derived classes生成copy...
#include<iostream>classMyClass{public:constinta=1;intb=0;MyClass(intaa,intbb):a(aa),b(bb){}MyClass(constMyClass&m){a=m.a;// 无法编译 error: assignment of read-only member ...b=m.b;}};intmain(){MyClassobj1(2,3);MyClassobj2(obj1);std::cout<<obj2.a<<" "<<obj2.b<...
A { std::string s2; // implicitly-defined copy assignment }; struct C { std::unique_ptr<int[]> data; std::size_t size; // user-defined copy assignment (non copy-and-swap idiom) // note: copy-and-swap would always reallocate resources C& operator=(const C& other) { if (this ...
C() { } }; int main() { B x, y; x = y; A w, z; w = z; C i; const C j(); // i = j; } The following is the output of the above example: A::operator=(const A&) A::operator=(A&) The assignmentx = ycalls the implicitly defined copy assignment operator ofB, wh...
Both the assignment operation and the initialization operation cause objects to be copied. Assignment: When one object's value is assigned to another object, the first object is copied to the second object. Therefore, c++ Point a, b; ... a = b; ...
如上述代码,当任何人(包括member函数或friend函数)尝试拷贝Test对象时,编译器便试着生成一个copy构造函数和一个copy assignment操作符. 编译器自动生成这些函数时,会调用其基类的对应函数,而基类中这些函数是private,因而那些调用会被编译器拒绝,产生编译器错误. ...
(2) 当一个 class 的base 有一个copy assignment operator时。 (3) 当类声明了任何一个virtual functions时。 (4) 当class继承自一个virtual base class时 2. 合成示例 1//Pseudo C++ Code: synthesized copy assignment operator 2inline Point3d&Point3d::operator=( Point3d*constthis,constPoint3d&p ) ...
To exercise the constructors, cctest first creates an instance of CMainClass using the default ctor, then creates another instance using the copy constructor:Copy CMainClass obj1; CMainClass obj2(obj1); Figure 1 Copy Constructors and Assignment OperatorsCopy ...