Can I determine if a templated class has a particular constructor, in my case using a string within function to which T is used?
Code:
template<class T>
void MakeObject(std::vector<T>& dataVector)
{
std::string str "con string,Joe,24";
// catch if T has string constructor
T someObject(str); // T someObject should have constructor from string
dataVector.push_back(someObject);
}
I would like to define a templated class while implementing default value on templated arguments. I don't know how to do that with string templated variables.
For exemple:
Code:
template <class T>
class A {
public:
A() { version = ???? }
std::string_base<T> version;
};
I don't want to pass the default value as parameter of the constructor. how I can do this?
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
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
I've this variadic template class implementation:
// Predefine template delegate factory
template < typename R, typename... Args >
class brGenericDelegate ;
// C++11 template alias to announce functor definition
template < typename R, typename... Args >
using brGenericDelegateType = std::function< std::shared_ptr<R>(Args...) > ;
[code]....
This template works fine for me. Now I have to compare, if the functors of the generic templates are equals ore not. Actually I see no way to reach this aim, because I've to cast the brDelegate on each request.
I'm trying to make an templated class of List and trying to make a list of Students(another class) which I made. Its not working.
Code seems to work fine for pre-defined data types but it crashes when it comes to students. I also want to run sort function on list of students.
Is this example correct? This example from a book
Constructor of the Base Class
Person::Person(char* n="", char* nat="U.S.A", int s=1)
{
name = n;
nationality = nat;
sex = s;
}
Constructor of the Derived Class (inherited from the base class)
Student(char* n, int s=0, char* i=""):
Person(n, s)
Why the initialized list of the base class constructor doesn't match the initialized list of the derived class constructor? I know this book is a little bit old, I'm not sure if this wrong in VC++ 2010?
I want to specialize a particular function for Integer datatype inside a class template. My XX.h will be
namespace ZZ {
template <class T>
class XX {
void doSomething(T x);
};
}
provide me XX.cpp which has template specialization for the function doSomething on Integer datatype.
I tried the following in XX.cpp
#include "XX.h"
using namespace ZZ;
template <class T>
void XX<T>::doSomething(T x) {
[Code] ...
But this code is not working.
to initialize this object? Why C++ FAQ says no? Here is my code,
Code:
class A
{
public:
A(int x, char c);
A(int x);
[code] ....
I don't have any trouble to call the constructor A(int x, char c) from another constructor A(int x).
Let's say I have a Car object , and it contains inner Engine object.
Code:
struct Car{
Engine mEngine;
};
In order to initialize the engine object NOT by the default constructor (if it has any) , we use initialization semantics:
Code:
Car::Car:
mEngin(arg1,arg2,...)
{
other stuff here
}
Now it gets tricky: Let's say a Car objects has 10 inner objects, each object has about 5 variables in it . Car is a base class for , e.g. , Toyota class. you don't want the Car class to have a constructor with 50 arguments. Can the inner objects of Car be initialized from the base class , e.g. Toyota?
Code:
class Toyota:
Car(...),
mEngine(...),
mGear(..)
{
...
};
The other options are:
1) like said , create a Car constructor which gets 50 arguments, then initialize Car as whole from Toyota - the code becomes less readable and less intuitive
2) Car constructor which get built-objects as arguments and initialize the inner objects with copy constructor . the code gets more readable but then you create many excess objects .
I understand it is done like this
// Calling the base class constructor
explicit CCandyBox(double lv, double wv, double hv, const char* str="Candy"): CBox(lv, wv, hv)
{
...
}
But how does the compiler know that you are initializing the base "part" of the object?
Or is this the entire reason initialization lists exist, to separate this confusion?
I am trying to use constructor within constructor in the same class. Is that possible. I have tried something and it shows me a error message:
error: type "mainClass" is not a direct base of "glavna"
This is the program I tried:
Code:
class mainClass {
private:
int x,y;
Code] ......
Suppose I have two classes A and B so how to access object of class A in constructor of B's class as a parameter.
View 6 Replies View RelatedI really confused with constructor (default constructor and constructor with parameters)
I coded this problem
and I worked almost, but I stock in constructor
Code:
class Tier {
public:
enum TIER_MAKE
[Code] ....
This is tier class and I have to finish constructor in class car (for simple, I skip detail code) -red things are the parts from class Tier
Code: Car()
: make(NULL), passengers(0), fuelcap(0.0), efficiency(0.0), tier(Tier::nexen)
{ }
[Code] ....
And someone said default constructor part has to be this
Code:
car( Tier::TIER_MAKE p_tiermaker = Tier::nexen )
//after i skip
but default constructor should be no parameter...? isn't it?
# include <iostream>
# include <cstring>
#include <iomanip>
#include <cmath>
using namespace std;
class Course
// Creating the class Course
[Code] ....
Errors: Warning1warning C4996: 'strncpy': This function or variable may be unsafe. Consider using strncpy_s instead. To disable deprecation, use _CRT_SECURE_NO_WARNINGS.
[Code] .....
I have to create an Array of type Course and then fill its member dats using various member functions. Those errors are caused by some Constructor defect, which I dont really know what it is.
I recently designed a struct like this
// MyMap.h
typedef std::map<std::string, std::function<void ()>> MyMap;
extern MyMap g_mymap;
// MyMap.cpp
My Map g_mymap;
[Code] ....
It looks useful to implement strategy pattern because it makes a fully separate code block. So I can add a function to the map simply by compiling a source file. It's very simple. I don't need to edit another file.
But when I use it for my existing project, It makes some linking and runtime errors.(vs 2012). I can't recognize exactly why because it is a huge project. Anyway, I have a question that - Is this a safe use of class constructor?
I know that there is no fixed order of running, but in this case I think it doesn't matter. because they are independent. But it is not a common pattern, so I can't decide to use it.
This is my class there is a problem with my copy constructor .. is that correct ??
struct Node {
Type info;
Node<Type> *next;
};
template <class Type>
class Queue
[Code] ....
Firstly I don't really know if this is possible.
This is my Class Diagram: [URL]...
github: [URL]...
I want to redefine the price object of the Book Class. However price is defined at Products Class.
I want the price value change according to the marker value, which is a Book attribute.
If the marker is blue, price gets a value of 10 (e.g.), if it has another value, price is equal to 20.
Basically, I need to set a variable outside of the constructor and make it accessible to the entire class.
It would need to work something like this:
#include <iostream>
#include <string>
template <typename MT> class CallbackFunction
{
[Code].....
I am making a snake game just to give some context.
//LevelObject.hpp
class LevelObject {
public:
virtual void Update() = 0;
virtual void Draw(Canvas& canvas) = 0;
protected:
Vector3 location_;
[Code] ....
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.
When the below is done, does it call the constroctor only, and if yes, constructors do not have return types so how does it work? is there anything behind the scene?
wxAddHandler(new wxPNG_HANDLER);
and
sf::RenderWindow(sf::VideoMode(...),...);
I am unable to understand how a move constructor works in this example of code. If someone could break down the process of what is taking place and explain to me on why to use a move constructor.
Code:
class MyString {
MyString(MyString&& MoveSource) {
if( MoveSource.Buffer != NULL ) {
Buffer = MoveSource.Buffer; // take ownership i.e. 'move'
MoveSource.Buffer = NULL; // set the move source to NULL i.e. free it
}
}
};
Example from "SamsTeachYourself: C++ in One Hour a Day"
I keep getting following errors:
multiple definition of `SDL2Graphics::SDL2Start()'
undefined reference to `SDL2Graphics::SDL2Graphics()'
My set up is as follows:
Main.c++:
#include <iostream>
#include "GL/gl.h"
#include "GL/glu.h"
#include "SDL2graphics.c++"
/* Global variables */
int main(int argc, char* argv[]) {
[Code] ....
I am trying to pass an object to an inherited clas by a constructor. I am having Cboard my board and i need to pass it to the object Cpawn.
Here under is my code:
main
Code:
#include<iostream>#include "Cboard.h"
#include "Cpawn.h"
#include "Cpiece.h"
void main(){
char location[50];
[Code] ....
I have three classes 1 base and two inherited.. problem is when I try to initialize the it says undefined reference to vtable constructor.
Code:
#ifndef QUOTE_H_INCLUDED
#define QUOTE_H_INCLUDED
#include <string>
using namespace std;
[Code] ....
I'm trying to make a class constructor within a namespace and I keep getting errors like: "'<variable>' is a nonstatic data member of class '<class>'" for when I try to setup parameters, and "Incomplete type is not allow" whenever I try to write out my function definition. Here's what I'm doing:
namespace test {
class blah;
} class blah {
typedef int var[5];
[Code] .....
Also I'm unsure why there is a parameter of 'const blah &' when I mouse over blah(); (using Visual Studio 2010) within the class definition. It tells me 'blah::blah(const blah &)' and I am unsure where the parameter comes from. How can I resolve these issues?