polymorphism

问题 One of my friends asked me "How Runtime Polymorphism is achieved in C++?" I answered "By Inheritance" He said "No, it can be achieved only using virtual functions". So I gave him an example of the following code :- #include<iostream> using namespace std; class A { public: int i; A(){i=100;} }; class B : public A { public: int j; B(){i = -1; j = 99;} }; void func(A& myA) { cout<<myA.i << endl; } int main() { B b; A* a = new B(); func(*a); func(b); delete a; return 0; } Here, function func()

问题 I've just started using JAXB to make XML output from java objects. A polymorphism exists in my java classes, which seems to not working in JAXB. Below is the way how I tried to deal with it, but in the output I haven't expected field: fieldA or fieldB. @XmlRootElement(name = "root") public class Root { @XmlElement(name = "fieldInRoot") private String fieldInRoot; @XmlElement(name = "child") private BodyResponse child; // + getters and setters } public abstract class BodyResponse { }

问题 I've just started using JAXB to make XML output from java objects. A polymorphism exists in my java classes, which seems to not working in JAXB. Below is the way how I tried to deal with it, but in the output I haven't expected field: fieldA or fieldB. @XmlRootElement(name = "root") public class Root { @XmlElement(name = "fieldInRoot") private String fieldInRoot; @XmlElement(name = "child") private BodyResponse child; // + getters and setters } public abstract class BodyResponse { }

问题 I am trying to emulate polymorphism through ES6 Classes, in order to be able to better understand this theory. Concept is clear ( designing objects to share behaviors and to be able to override shared behaviors with specific ones ) but I am afraid my code above is not a valid polymorphism example. Due to my lack of experience, I appreciate if you answer these questions in a comprehensive way: The fact that both Classes have an equally named method, and that instances made from each Class get

问题 I've just started using JAXB to make XML output from java objects. A polymorphism exists in my java classes, which seems to not working in JAXB. Below is the way how I tried to deal with it, but in the output I haven't expected field: fieldA or fieldB. @XmlRootElement(name = "root") public class Root { @XmlElement(name = "fieldInRoot") private String fieldInRoot; @XmlElement(name = "child") private BodyResponse child; // + getters and setters } public abstract class BodyResponse { }

问题 I am trying to emulate polymorphism through ES6 Classes, in order to be able to better understand this theory. Concept is clear ( designing objects to share behaviors and to be able to override shared behaviors with specific ones ) but I am afraid my code above is not a valid polymorphism example. Due to my lack of experience, I appreciate if you answer these questions in a comprehensive way: The fact that both Classes have an equally named method, and that instances made from each Class get

问题 I am trying to emulate polymorphism through ES6 Classes, in order to be able to better understand this theory. Concept is clear ( designing objects to share behaviors and to be able to override shared behaviors with specific ones ) but I am afraid my code above is not a valid polymorphism example. Due to my lack of experience, I appreciate if you answer these questions in a comprehensive way: The fact that both Classes have an equally named method, and that instances made from each Class get

问题 I am trying to understand the real requirement of the usage of templates for policy based design. Going through the new templated designs in C++ I found that policy based class design is a highly suggested way of design which allows you to 'plug-in' different behaviors from policy classes. A minimal example is the following (a shortened version of the wiki): template <typename LanguagePolicy> class HelloWorld : private LanguagePolicy { using LanguagePolicy::message; public: // Behaviour

问题 This question already has answers here : When should static_cast, dynamic_cast, const_cast and reinterpret_cast be used? (9 answers) Closed 6 years ago . In C++ we can convert child class pointer to parent, but is there any way to convert it back: from parent, which was obtained from child, give child class back? I mean: class Parent { ... }; class Child : public Parent { ... }; int main(int argc, char const *argv[]) { Child* child = new Child(); Parent* parent = child; Child* old_child =

问题 This question already has answers here : When should static_cast, dynamic_cast, const_cast and reinterpret_cast be used? (9 answers) Closed 6 years ago . In C++ we can convert child class pointer to parent, but is there any way to convert it back: from parent, which was obtained from child, give child class back? I mean: class Parent { ... }; class Child : public Parent { ... }; int main(int argc, char const *argv[]) { Child* child = new Child(); Parent* parent = child; Child* old_child =