inheritance

问题 I'm having trouble passing a derived class to a function which accepts the base class as argument. The base class is consists of "obstacles" which are to be placed on a "board" void Board::setvalue(int length, int width, Obstacle& obstacle); However, this causes the compiler to give the "no known conversion for argument..."-error. Reading up around the site i found that i should be passing the derived object as a const, this however causes problems because a const can't be assigned to the

问题 I'm having trouble passing a derived class to a function which accepts the base class as argument. The base class is consists of "obstacles" which are to be placed on a "board" void Board::setvalue(int length, int width, Obstacle& obstacle); However, this causes the compiler to give the "no known conversion for argument..."-error. Reading up around the site i found that i should be passing the derived object as a const, this however causes problems because a const can't be assigned to the

问题 I'm using class attributes as a neat way to keep common strings used throughout my project. Parent class has an 'main' attribute that is used to compose other attributes. Some of use cases need to use child class with this 'main' attribute changed. How can I force the child class to run the parent class attributes initialization for not-overridden attributes? Basically, I want this code to work: class One: MAIN_ATTR = 'one' COMPOSED_ATTR = ' '.join([MAIN_ATTR, 'composed']) class Two(One):

问题 I'm using class attributes as a neat way to keep common strings used throughout my project. Parent class has an 'main' attribute that is used to compose other attributes. Some of use cases need to use child class with this 'main' attribute changed. How can I force the child class to run the parent class attributes initialization for not-overridden attributes? Basically, I want this code to work: class One: MAIN_ATTR = 'one' COMPOSED_ATTR = ' '.join([MAIN_ATTR, 'composed']) class Two(One):

问题 I'm using class attributes as a neat way to keep common strings used throughout my project. Parent class has an 'main' attribute that is used to compose other attributes. Some of use cases need to use child class with this 'main' attribute changed. How can I force the child class to run the parent class attributes initialization for not-overridden attributes? Basically, I want this code to work: class One: MAIN_ATTR = 'one' COMPOSED_ATTR = ' '.join([MAIN_ATTR, 'composed']) class Two(One):

问题 I know how virtual works in the context of member functions, but I saw an article online about virtual member classes that confuses me. The example I found is this: class Machine { void run () {} virtual class Parts { }; }; // The inner class "Parts" of the class "Machine" may return the number of wheels the machine has. class Car: public Machine { void run() { cout << "The car is running." << endl; } class Parts { int get_Wheels () { cout << "A car has 4 wheels." << endl; return 4; } string

问题 Suppose I use the fairly common idiom to define struct inheritance in my_header.h : struct A { int a_field; ... }; struct B { struct A _as_A; int b_field; ... }; Now in my C code I can do binstance._as_A.a_field , or I can cast a pointer to B to a pointer to A, and so forth. My question is this. Suppose that I now define a new C++ header my_header.hpp : struct A { int a_field; ... } struct B : A { int b_field; ... } Suppose I do this taking care to make sure B is a POD type . Am I guaranteed

问题 I know how virtual works in the context of member functions, but I saw an article online about virtual member classes that confuses me. The example I found is this: class Machine { void run () {} virtual class Parts { }; }; // The inner class "Parts" of the class "Machine" may return the number of wheels the machine has. class Car: public Machine { void run() { cout << "The car is running." << endl; } class Parts { int get_Wheels () { cout << "A car has 4 wheels." << endl; return 4; } string

问题 This question already has an answer here : What happens in the heap when class A inherits class B in Java (1 answer) Closed 1 year ago . Consider a Superclass A and a derived class B whereas A contains a private variable x . B contains an explicit super() call as first argument inside its constructor while there might be some other variables of B like y and z . As far as I know there is no inheritance for private fields. Does that mean private fields will not get instantiated while executing:

问题 Here I am trying to include a class file into another class file like <?php include './connection.php'; class header_class extends connection { } and in connection.php <?php class connection { //put your code here } both the files are in same folder called classes now when i am trying to extend connection class in header_class . Its give an fatal error. ( ! ) Fatal error: Class 'Connection' not found in D:\Projects\wamp\www\Session-6\classes\header.php on line 4 Call Stack # Time Memory