C++ :: Change Behaviour Of Template Class Depending On Type?
Jul 8, 2012
is there a way to have a template class respond to missing stuff in a template type ?
Code:
template <typename Type>
class MyClass
{
public:
enum { ID = Type::ID }; // revert to 1 if Type::ID doesn't exist.
};
If the Type passed to the template has an ID member (required to be an enum or a static const int), use it, if it is missing revert to a default value.
I can use this as a simplified way of configuring how MyClass works, without requiring Type to explicitely needing to define what it doesn't care about.
It needs to be resolved at compiletime, as it determines the number of elements in member array variables.
/** This class build the singleton design pattern. Here you have full control over construction and deconstruction of the object. */ template<class T> class Singleton
[Code]....
I am getting error at the assertion points when i call to the class as follows:
I am trying to pass a class as a type to a template class. This class's constructor needs an argument but I cannot find the correct syntax. Is it possible?
Here is an example of what I described above. I did not compiled it, it is for illustrative purpose only. And of course argument val of the myData constructor would be doing something more useful than simply initializing an int....
template <class T> class templateClass { templateClass() {};
[Code]....
My real code would only compile is I add the myData constructor:
myData () {};
and gdb confirmed that it is this constructor that get called, even with dummy(4).
Okay, I've been working on this Texture class that's going to be compatible with both SDL and OpenGL with the capability to create an array of textures within one class as opposed to multiple classes and such.
Now I've run into a slight issue if I want to return the value of a texture. There's two different types of textures: SDL_Texture, and a standard GLuint Texture. The problem I have is that one or the other is used, not both which is depending on whether or not the person is using OpenGL.
So when the user wants to get the texture, I need the ability to return either an SDL_Texture, or GLuint depending on whether or not OpenGL is being used.
I tried this with a template class, but it didn't work, but I'll post the code so you can see what I'm trying to do.
It basically just comes down to the last four lines of code. If the person is Using OpenGL return a GLuint, if the person is using SDL, return an SDL_Texture.
I would prefer to have the GetTexture function to be one function instead of two separate ones so I don't have to call a different function every time to check if I'm using SDL or OpenGL.
I have a class "Result" with a single template function Set(const std::string& arName, T& val) and a specialization of this function Set<Real>(const std::string& arName, Real& val) where Real is a typedef for double. The class is in a shared library and I use it in my main program. If I do result->Set<GLOBAL::Real>("U", 100.0); the wrong template function is called!
I check this by the output with std::cout.
Maybe it's a problem with the typedef.
If I link the object file of the Result class directly to my main program (no shared library), it works.
Here's the problem I want to intialise different classes based on user input. I've tried using an IF statement but the scope of an if statement would mean the rest main program wouldn't be able to see it.
I have `MainShop`(base class) then `SwordShop` and `BowShop`(derived classes) and another derived class called `Inventory`. I have a vector under protected in my base class, and when I access it from my derived classes it's okay, but each one has its own value. How can I set them all to have the same value?
//MainShop.h #pragma once class MainShop { private: //some variables protected: vector <string> WeaponInventory;
[code]......
Here every time I run it, it goes straight to the `else` and it displays that I do not have any items. I want to just have one vector for both my bow and Sword shops because vectors take up a lot of memory and my teacher said keep them to a minimum. So I just want one vector that takes in items from my bow class as well as my sword class, but for some reason it's acting as if I have multiple vectors, each with its own set of items.
I'm trying to implement a simple template array class, but when i came into the operator< i actually have to use a template :
my code is something like :
template<typename _Type, std::size_t _Size> class array { public :
[Code] ......
but i am having an error of shadows template param 'class _Type' is it w/ the name conflict between the array template parameter and the function template parameter ?
Error1error C2955: 'DoubleLinkedListInterface' : use of class template requires template argument listdoublelinkedlist.h10 Error2error C2244: 'DoubleLinkedList<T>::DoubleLinkedList' : unable to match function definition to an existing declaration doublelinkedlist.cpp7
Error3 .cpperror C2244: 'DoubleLinkedList<T>::~DoubleLinkedList' : unable to match function definition to an existing declaration 12
.h
#pragma once #include "DoubleLinkedListInterface.h" #include "Node.h" #include <iostream>
I have a generic template class with another template in one of its types. Now I want to specialize one of its methods for a particular (template) class, which leads to a compile error, however.
GCC ends with: :35:27: error: type/value mismatch at argument 2 in template parameter list for ‘template<class Type, template<class> class O> class Foo’ :35:27: error: expected a class template, got ‘Obj2<Type>’
What is wrong with the specialization? Can it even be achieved and how (if so)?
how I want the code to look. Only problem is it doesn't work (Line 11). I have some experience with templates but I'm not a pro.
Basically I want the "Channels<3>" to be a type that I can use to specify a Cable with similar to vector<float/int> it would be Cable<Channels<2 or 3>>.
What have I messed up with the syntax?
#include <iostream> #include <vector> using namespace std;
I would like to use my own template type. I have class Fraction that saves fractions, and class Sample(the template class) that arrange fractions in order.
I've been pondering which of these 2 approaches would make for the best interface for a library: Defining custom exceptions with specific names for different error scenarios but with standard behaviour, or simply using the predefined exceptions from the STL.
This is my current approach: Code: namespace rpp { class ConnectionError : public std::exception { public: ConnectionError(const std::string &p_err);
[Code] .....
This seems to make for more descriptive code but it adds no functionality and the implementations are completely identical, which seems "off" to me, somehow.
When I ran it only the calls from doers array is called 7 times normally, and donters only one time. Why is that? When I call doers from the second loop, it prints the doers functions again....and only one call to donters is made to the first static inline donter functions __dont1()...
I am an IT student currently learning linked list. I have a problem with my code here. After I call addFront() my list doesn't change when I display it. How do I somewhat change/fill my list without changing the function type? I know it works on pointers still messed up with linked list.
Is there a way to detect whether or not a template type has a protected destructor?
I see there is std::is_destructible in C++11, but I can't tell if this will return true or false for the protected case. Also, I'm interested in finding a solution for C++03 as well.
