C++ :: Passing Class As Type In Template Class
Nov 30, 2013
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).
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Oct 12, 2013
Let me put it into the code snippet:
/**
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:
osgOpenCL::Context *cxt = osgOpenCL::Singleton<osgOpenCL::Context>::getPtr();
I tried commenting assertion statements and then the debugger just exits at the point where getPtr() is called.
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Oct 7, 2014
How to initialize a static member of a class with template, which type is related to a nested class?
This code works (without nested class):
#include<iostream>
using namespace std;
struct B{
B(){cout<<"here"<<endl;}
};
template<typename Z>
[Code] ,....
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Aug 15, 2012
I have in the past written code for templated functions where one function argument can be either a function pointer or a Functor. Works pretty straightforward.
Now I am in a situation where I am actually trying to pass a function pointer as template argument to a class. Unfortunately this does not work, I can pass the Functor class but not the function pointer. Below code illustrates the issue:
Code:
#include <string>
#include <iostream>
#include <sstream>
#include <cstdlib>
// For demonstration
const char * external_library_call() {
return "FFFF";
[Code] .....
The idea is to have the definition of the Record class simple and readable and have a maintainable way to add auto-conversion functions to the class. So the lines I commented out are the desirable way how I want my code to look. Unfortunately I could not come up with any way that was close to readable for solving this.
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Feb 4, 2015
For example I want to get the type of std::vector<>::size_type without specifying a template argument.
Here's what I want to do:
std::vector<>::size_type x{5};
Is there any way this can be done?
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Jun 25, 2013
I'm getting unresolved link errors when I attempt to compile.
dNode.h
#ifndef DNODE_H
#define DNODE_H
template <class T>
class dNode {
[Code] ....
ERROR:
Error1error LNK2019: unresolved external symbol "public: __thiscall dStack<double>::dStack<double>(void)" (??0?$dStack@N@@QAE@XZ) referenced in function "void __cdecl stack_test(void)" (?stack_test@@YAXXZ)main.objprog09
Error2error LNK2019: unresolved external symbol "public: virtual __thiscall dStack<double>::~dStack<double>(void)" .......
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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.
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Jul 19, 2013
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.
typedefs.hpp:
namespace GLOBAL {
typedef double Real;
} results.hpp
#include <iostream>
[Code] ....
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Sep 23, 2012
Code:
template<class T>
class Convert {
T data;
public:
Convert(const T& tData = T()) : data(tData)
[Code] ....
Why do we use operator? Is float and double function names below?
Code:
Convert<int>::operator<float> float();
Convert<int>::operator<double> double();
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Dec 9, 2014
I'm making a minimal spanning tree class that inherits a graph class, both are templated. This is my mstree.h so far:
#ifndef _MSTREE_H_
#define _MSTREE_H_
#include "graph.h"
namespace MSTreeNameSpace
[Code]...
and I keep getting these errors:
mst.h:9:25: error: expected template-name before ‘<’ token
class MST : public Graph<T>
^
mst.h:9:25: error: expected ‘{’ before ‘<’ token
mst.h:9:25: error: expected unqualified-id before ‘<’ token
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Dec 14, 2014
im passing a vector of a class to a function of another class. But i cant access the data on the classes inside the vector.
Something like that:
class CDummy{
...
public:
string m_name;
[Code].....
Im creating the vector on main() and using push_back with a pointer to an initialized CDummy instance
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Feb 3, 2013
I'm trying to template the return type for this function (component), I've looked around for example code but there doesn't seem to be any exactly like what I want.
Entity.hpp
class Entity {
public:
Entity();
unsigned int id = 0;
Component& addComponent(std::string);
[Code] ....
Error : 'ent1.component<HealthComponent>' does not have class type
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Dec 5, 2013
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 ?
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Nov 6, 2013
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>
[Code]....
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May 27, 2013
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.
Here is the example:
#include <stdio.h>
template<typename Type>
class Obj1 {
public:
void ID() { printf("Object 1, size = %zu
[Code] .....
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)?
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Nov 2, 2014
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;
[Code].....
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Feb 9, 2015
I have a class like this
PHP Code:
template<class X>
class A {
X m_x;
public:
X* foo();
X* bar();
//others are not related to X
};
I would like to get rid of
PHP Code: template<class X>
For class level but still use it for members. Like this
PHP Code:
class A {
X m_x;
public:
template<class X>
X* foo();
template<class X>
X* bar();
//others are not related to X
};
However, I am still stuck at
PHP Code: X m_x;
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Feb 4, 2014
std::cout << "Hello C++ programmers!" << std::endl;
I am trying to create a LinkedList (and then, an ADT stack; // yes, I cannot use the STL stack because the teacher won't let me), and I am getting some weird error when I create a ListNode and declare LinkedList (which has the ListNodes!) a friend of it.
Here is my header-file code for both classes:
ListNode.h
#ifndef LISTNODE_H
#define LISTNODE_H
#include "LinkedList.h"
[Code]...
The errors I am getting are:
error: 'LinkedList' is not a class template
I have tried forward-declaring LinkedList in the ListNode.h file, but I get this error:
error: 'ListNode' does not name a type
Are there any other possible solutions to this problem; // without having to resort to crazy stuff like having a .h file #include a .cpp file, or even declaring and defining ALL OF MY CODE in the .h files???
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Mar 3, 2013
I have this class templates And This UML.I have to write this function +operator=(source: Array<ElemType, SIZE>): Array<ElemType, SIZE> but I do not know how to start the declaration / or start the function. I have to return a template but I do not know how to do it,
UML
Array<ElemType, SIZE>
-elements: ElemType[SIZE]
+Array()
+Array(source: Array<ElemType, SIZE>)
+operator=(source: Array<ElemType, SIZE>): Array<ElemType, SIZE>
+operator==(other: Array<ElemType, SIZE>): Boolean
+operator!=(other: Array<ElemType, SIZE>): Boolean
<<L-value>>+operator[](index: Integer): ElemType
<<R-value>>+operator[](index: Integer): ElemType
[code]....
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Feb 3, 2013
I want to use a template function of a class.
This is my code:
#include "Comparison.h"
#include <iostream>
using namespace std;
int main(int argc, char** argv) {
Comparison c;
[Code] ....
But I get the error message:
main.cpp:10: undefined reference to `int Comparison::max<int>(int, int)'
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Mar 22, 2013
refer to the code below, the attribute class is created with the value type and default value, but why it doesn't work for std::string?
#include <string>
#include <iostream>
using namespace std;
[Code].....
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Sep 13, 2014
The code below references to a header file and implementation .cpp file, which are not important. My question is what is the proper way to use a constructor in a main file. I have been getting "invalid use of" errors when using letters.Pair(a,b), where Pair(T a, T b) is a constructor that accepts arbitrary type T of variables 'a' and 'b'. So I played around a bit and suddenly found a syntax that works. I need verification for the syntax below:
#include <iostream>
#include "pair.h"
#include "pair.cpp"
[Code].....
Are the comments with the asterisks correct? As in this is always the way you initialize and assign? So letters.Pair(a, b) is not the right way to use constructors?
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Jun 3, 2014
I have the following class header in library, but when i initialize in main the class, i have an error unresolved external symbols. So the class is not exported as it should.
Code:
template <typename Key, typename Value>
class UTILITIES_EXPORT MyMap : public QMap<Key, Value>
{
public:
MyMap() : QMap<Key, Value>() { }
[Code]....
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Dec 5, 2013
The following program is designed to demonstrate class templates. The program will evaluate postfix expressions input to the console by pushing them in a stack, and then popping them and evaluating them as such, (ex. entering 3 4 + would equal 3+4 = 7).
The code is below. We are not to modify it, but to fill in the blanks, the places filled in indicated with two asterisks for a line, and one on each side for a part of a line. If I didn't know what to enter (if anything), I put three ?s. If you want to copy and compile for yourself, look for all the *s and ?s.
1) I'm turning up all sorts of errors in the main program file (prog5.cpp) having to do with stacktype.cpp. It has been removed from the program, as it is included at the end of stackType.h. Most of them are "cannot convert 'this' pointer from StackType to StackType<stack> &'. How do I fix that?
2) The program supposedly lacks a default constructor, and it keeps turning up that 's' is an array of unknown size (do I call StackType or stack or what?).
stackType.h Code: #pragma once// Catherine Stringfellow and Trey Brumley
// A Stack is a data type, which stores values in an order where values are added to the top of the stack when pushed,
// and when popped, remove and return the value from the top of the stack.
// Class specification for Stack ADT in file StackType.h
using namespace std;
static const int MAXITEMS = 50;
[code].....
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Apr 25, 2013
I have a list of numbers in an array created by a class template
Code:
#include <iostream>
#include <fstream>
#include <string>
#include <iomanip>
using namespace std;
const int CAPACITY = 20;
template <class T>
class A
[code].....
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Apr 15, 2014
I want to have a template function that is a member of a class. Is this possible? This code snippet is how I would think the syntax would go, although it doesn't compile. How would I achieve the same effect?
Code:
class myclass {
public:
int member ;
} ;
template <typename T> void myclass::func( T& arg )
[Code] .....
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