nested-class

问题 This question has a detailed answer here: Overloading operator<<: cannot bind lvalue to ‘std::basic_ostream<char>&&’ I am trying to overload a nested subclass, and spent an hour trying to overload operator<< . Researched a little here, but still couldn't resolve it. Any help? :) Whenever I try compiling it using g++ -std=c++11 -lm -ggdb -g -O0 -Wall p_7_1.cpp -o p_7_1 , it gives me an error: Undefined symbols for architecture x86_64: "operator<<(std::__1::basic_ostream<char, std::__1::char

问题 I'm currently having an assignment, in which i need to create a DATABASE class, which contains a employees pointers array , and private inner class , that defines employees linked list the goal to accomplish here, according to the assignment, is working acording to a DB_TYPE defined constant. when DB_TYPE = 0 i need my class methods to work with the employees pointers array , when DB_TYPE = 1 i need my class methods to work with the employees linked list . Therefore, i need two things: 1.

问题 The thing that bothers me is the second point. I thought it might have to do with the fact that the "this" pointer isn't static and so the inner class can't access it. I'm not sure if that's the right explanation though. This also raised another question for me which was "where is the "this" pointer defined?" 回答1: The difference between a static nested class and one that isn't static is precisely that an instance of a non- static inner class is associated with a specific instance of the

问题 I am using Qt5 with the VS2013 compiler. I am trying to nest two classes CUDial and DUDial in the same outer class UDial . UDial is a QDialog type class. I would like CUDial and DUDial to be both of QWidget type. It for use with a QTabWidget variable in the outer class. So, I write the code as follow: class UDial : public QDialog { Q_OBJECT class CUDial : public QWidget { Q_OBJECT // Some variables public: CUDial(QWidget *parent = 0); }wid1; class DUDial : public QWidget { Q_OBJECT // Some

问题 I was reading Effective Java 2 - Item 22 and it says in the title: "Favor static member classes over non-static" but at the end of the chapter Implementations of the collection interfaces, such as Set and List, typically use nonstatic member classes to implement their iterators: // Typical use of a nonstatic member class public class MySet<E> extends AbstractSet<E> { ... // Bulk of the class omitted public Iterator<E> iterator() { return new MyIterator(); } private class MyIterator implements

问题 There is this code: #include <iostream> class Outer{ int a; // private data member of class Outer public: Outer(): a(55){} class Inner{ public: void fun(Outer ob){ std::cout << ob.a << std::endl; } }; }; int main() { Outer::Inner object; object.fun(Outer()); // prints 55 //std::cout << (Outer().a) << std::endl; error: 'int Outer::a' is private return 0; } Why Inner class has access to private member data 'a' of class Outer? Following this article XL C/C++ V8.0 for Linux, it should not compile

问题 Why is this? I would find it really nice to be able to have some extension methods locked down to be used only within one of my classes. Don't really want to have certain extension methods available everywhere... and they look so much nicer than regular static methods :P For clarification: The reason I want these extension methods is because I am extending a Form, which has a DataGridView on it. And I am getting very tired of lines like these: foreach(var row in grid.Rows.OfType

问题 I want to know how many instances of a static member class can be created by the enclosing class. I assume one only, but then the following extract from Bloch doesn't make sense to me. Quoting Joshua Bloch's Effective Java - Item 22*: Favor static member classes over nonstatic. A common use of private static member classes is to represent components of the object represented by their enclosing class. For example, consider a Map instance, which associates keys with values. Many Map

问题 Can a DataTemplate in XAML be associated with a nested class? I am working on a MVVM application, and I have run into a data template problem. I have a view model providing a collection of other view models for an items control. These items are part of a hierarchy defined as nested classes in the outer view model. I have been unable so far to create a mapping in XAML to reference the inner nested class. Here is the class hierarchy (simplified for brevity): public class MainViewModel { public

问题 I have the following nested viewmodel class... public class CustomerModel { public string name; public Address mailingAddress; public Address billingAddress; } public class Address { public string line1; public string city; public string country; } I was hoping that there is some automated way to create an edit page, but everything that I've tried and read indicates that the framework and code-generates only handle top level properties in your viewmodel. The 'name' property is the only one