class Element {
public:
..
virtual unsigned NumberOfNodes() = 0;
[Code] ....
Is it possible to implement this better? All the element stuff can be static, but this is not possible with the abstract class. I want to have Mesh independent of a specific element. With the code above, if I have multiple meshes I have one instance of an element, e.g., Triangle for each mesh. Although they are all exactly the same.
A have two classes, one inheriting the other, and the parent class being abstract (I plan on adding more child classes in the future). For reasons I won't bother mentioning, I'm making use of an STL container as a way for me to access all of the child objects in the heap. I've done so by making use of a map, with key type int and value type being a pointer to the parent class:
//PARENT.H class Parent { protected: static int n; static std::map<int, Parent*> map; public: virtual void pureVirtual() = 0;
[code]....
The Problem:In line 5 of Parent.cpp, initializing the value of the element to new Child won't work, as according to the compiler, the Child class hasn't been declared yet, and including Child.h into the Parent.h only opens an even bigger can of worms.I also can't initialize it as new Parent, seeing as the parent class is an abstract one.
The Question:Is there a way I can initialize the static map properly. Making the Parent class abstract is not an option.
For example, in a header file A.h, I define an abstract class,
Code:
// A.h class A { public: virtual void foo() = 0; private: static int _x; };
How'd I initialize static member data _x?Normally, we initialize a static member data in a cpp file. However, there is not cpp file for A.h. If I intialize _x in header file, there will be linker errors like mulitple defined symbols. What is appropriate way to do that?
I have an abstract base class - let's call it MyInterface - and a class that most classes in my program inherit from, let's call it MyBaseclass.
Let's assume that all my objects inherit MyBaseclass, some of which also inherit MyInterface. Now I want to collect objects in a container class, MyContainerclass. The container class is only interested in objects that implement MyInterface.
Now I know that all objects that inherit MyInterface also inherit MyBaseclass, but the compiler doesn't know that. MyContainerclass wants to call methods in MyBaseclass, but it collects pointers to MyInterface classes. I can't make MyInterface inherit MyBaseclass, because I will be using classes that I don't want to change (they are part of a framework) that already inherit MyContainerclass. IOW, I can't use virtual inheritance to get a nice inheritance diamond.
To sum up, I want to create a container class that:
1. Collects objects that implement MyInterface.
2. Calls MyBaseclass methods on the collected objects.
A static function can be called in relation to a particular object by a statement such as the following:
aBox.Afunction(10);
The function has no access to the non-static members of aBox. The same function could also be called without reference to an object. In this case, the statement would be:
CBox::Afunction(10);
where CBox is the class name. Using the class name and the scope resolution operator tells the compiler to which class Afunction() belongs."
1. Is that mean that Do() is only available for use by Dog itself because Dog is 'oryginal' Dog, and if i create new dogs - instances of oryginal Dog (dog1, dog2 ...) they cant access because Do is only available fo 'oryginal' one? Is that correct thinking?
2. If i would want to have something common (e.g value) for all dogs is that good way to create static field/method for Dog instead of non-static once then all instances of Dog would access Dog static member to get/change it? Just stupid example: static method GetAmountOfLegs() which return 4 Then all instances can take/call that value from Dog. Is that correct thinking?
I need to create a vector of pointers and hold the book objects in it. then i have a virtual function in my books which is a pure virtual in LibraryItems. When i try to add the books object in my code, i understand that since the scope runs out there is no object that is added. so when i run print it gives me an error.
#include<iostream> #include "books.h" #include "library.h" #include <vector> using namespace std;
int main(int argc, char * argv[]) { vector<LibraryItems* >libraryInfo;
I have this header file called Shape.h containing these function declarations. and a Shape.cpp which contains the body of the function. I am not showing it since it is not needed.
//This is from Shapes.h header file #ifndef SHAPES_H #define SHAPES_H #include <iostream>
[Code]....
I have this unfinished Main.cpp because the third line "JuanSanchez::Circle *pCar = new Circle; " is giving me a compiler error "error C2061: syntax error : identifier 'Circle' "
#include "Shapes.h" int main() { const int arrayIndex = 4; JuanSanchez::Shape *myShape[arrayIndex]; JuanSanchez::Circle *pCar = new Circle; }
I am working on a project that requires me to create objects from a abstract class that has 2 child classes (that need to be derived). Any examples on how to do this? I looked online and the examples were pretty vague. the main error that I am getting is when I make a temp object with & in front of it (such as Employee &genericEmp) it throws a must be initialized error.
I want to create an abstract base class having a member function that can accept a templatized structure as its parameter, something that according to C++'s rules can't be done for a good reason.
That good reason it is because an abstract base class is intended to provide interface rules to the classes that will derive from it and should not deal with data.
But how would you go about doing something like the following which is probably a reasonable design decision?
The problem I have is with the Size constructor and the abstract class LevelObject which size is a member of.
The compiler error I get is:
C:Program Files (x86)ProgrammingProjectsUniversityprg_interactivesnakey_takeysrc..inc..incPlayer.hpp|17|warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default]| C:Program Files (x86)ProgrammingProjectsUniversityprg_interactivesnakey_takeysrc..inc..inc..incPlayer.hpp|17|warning: non-static data member initializers only available with -std=c++11 or -std=gnu++11 [enabled by default]|
[Code] .....
However I do invoke the copy constructor when I pass a variable of type size to the constructor in this line:
size_ = Size(s);
But the problem is that its complaining that the abstract class LevelObject doesn't invoke the constructor, which it shouldn't.
I have an abstract class called Mbase and from it derived two classes: Sparse and Dense. Now I have an array in which its elements can be either Sparse or Dense. So, I delcared the array to have pointers to Mbase class. For example:
PHP Code: Mbase** A; Sparse* A1 = new Sparse; Dense* A2 = new Dense; A[1] = dynamic_cast<Mbase*>(A1); A[2] = dynamic_cast<Mbase*>(A2);
Now, I have operator + defined in Sparse and Dense. but when I do
PHP Code:
A[1]+A[2]
I get that operator + is not defined for Mbase class. So, I tried to define it in the Mbase class
However, the last code does not compile complaining that it cannot declare a class of type abstract in Mbase operator +(Mbase A). I think this is because I am returning Mbase instance.
I have an abstract class named Terrain, and a class named RoadMap, which supposed to hold an N*N array of Terrains. But I'm not sure what type should the RoadMap class hold:
Code: #ifndef TERRAIN_H #define TERRAIN_H class Terrain {
[Code] ....
I can't use an array of refernces here, so I tried this:
Code: Terrain** terrain; and then I thought this was the way to go:
Code: Terrain (*terrain)[]; But now I'm not sure.
The N*N matrix size supposed to be determined according to a given input... What type should I use there?
Imagine if there is an abstract class with a method (say output or print) which would be inherited by a few other classes. Later objects are created using the inherited classes, and the user wishes to call the above method twice, for eg (i) output/print to screen and (ii) output/print to a file. What is the best way to achieve that.
I'm trying to implement a decision tree that gets doubles as input (in this sample code just random numbers) and returns a boolean value. At the nodes, I'd like to use various operators that can have different input and return types. I've implemented an abstract base class for the nodes and I'm deriving the specific nodes from it. In the code below, I've included only a few derived classes. Building the tree (randomly) is no problem. However, I'm looking for a clever way to evaluate the tree. I think that uncommenting the lines in bold print would in principle do it. However, this is not possible because "value" is not a member of the base class. The type of "value" is different in the derived classes, so I cannot simply declare it in the base class.
"Node.h" #pragma once class NodeBase{ public: NodeBase* Child_1; NodeBase* Child_2; virtual void evaluate() = 0;
The abstract class can provide more functionality without affecting child classes.If we add any method to the interface ,then will it affect all the child classes ?
I have a class containing a map member that I want to initialize at declaration time. I know I can do it in the cpp file but I'm having a problem with the order of initialization (static initialization order fiasco).
My questions are:
Is it possible that the scenario in which, the Test's constructor's implementation and the map initialization instruction are in the same cpp file and constructor is called when the map is not initialized yet, could happen?
Is it possible to initialize the map in class like I did? I get these errors:
in-class initialization of static data member 'std::map<std::basic_string<char>, Test*> Test::a' of incomplete type temporary of non-literal type 'std::map<std::basic_string<char>, Test*>' in a constant expression
If yes, does this initialization resolve the static initialization order fiasco?
class Test { public: static std::map<std::string, Test*> a = {};//this is an error Test(std::string ID) {
I am developing logging class and it loos like below now, my question here is I would like to avoid situation to call this class methods multiple times in same time - as I've read when I have static class or even static method (not exactly whole class) it can be call only once in time. Is this true and whether my class would pass the concept to avoid multi accessing - lets say in case of multithreading case - if one task would try to call statuc method when there is already some other trad using it.
public static class Log { public static string EngineName { get; set; } private static List<String> logdata = new List<string>(); public static void LogMessage(string msg, ELogflag flag, string title = "") { StringBuilder sb = new StringBuilder();
I have started to move over to using Unicode, wide character null-terminated strings in my Windows programmes. Accordingly I set the Use Unicode Character Set Visual C++ compiler option. It is my understanding that once you do that the many macros which determine whether you transparently call ...A() or ...W() API functions automatically shift over to calling the wide character variants. As this is a compiler directive, all the choices are made and hardcoded in to the resultant executable at compile/link-time BEFORE it is ever run. Therefore using for example the macro OpenFileName() in the source code instead of specifically calling OpenFileNameW() has no impact on run-time performance.
The next logical step, instead of explicitly using wchar_t is to declare null-terminated string character arrays as TCHAR*. Then, so long as I also employ the tcn... variants of CRT string functions and call TEXT() or _T() macros to create string literals the preprocessor will chose, again transparently whether to create an executable using standard multibyte or unicode wide characters - and their associated functions - all determined by the Use Unicode Character Set switch. That way I can cover both eventualities with the same source code.
So, with all that - I THINK!!! - properly under by belt, I am fairly sure that using TCHAR and its friends will not effect run-time performance at all. However, in his otherwise excellent article the author makes it sound as if using Unicode EXPLICITLY through wchar_t, ...W() API functions and tcn... CRT calls is faster than the TCHAR alternative.
At the end of the day my question is - have I got the right end of the stick; TCHAR makes no difference to executable performance?
If I need a static pointer to a class that is used globally(multiple files), and I only want to allocate memory once.
One way is to create a function that returns a static pointer of type class and call it where ever you need this pointer. My question is there another way to do this like with a header file and include the header file where you need to use the object of type class.
static class* function { static class c; if (c == NULL) { c = new class; } return c }
