C++ :: Creating One Class Object In Constructor Of Another Class
Sep 20, 2013Suppose I have two classes A and B so how to access object of class A in constructor of B's class as a parameter.
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C++ :: Passing Object To Inherited Class By Constructor
May 1, 2013I 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] ....
C++ :: Constructor Exercise - Creating A Class Called Screen With Some Specifications
Feb 15, 2014This exercise is from C++ primer 5th edition. I have not understood everything about constructors, mainly about how they function.
Work prior to the exercise was creating a class called screen with some specifications. This is the class:
Code:
class screen{
public:
using pos = string::size_type;
screen() = default;
private:
pos height = 0;
pos width = 0;
pos cursor = 0;
string contents;
};
The exercise goes as follows:
Exercise 7.24: Give your Screen class three constructors: a defaultconstructor; a constructor that takes values for height and width and initializes the contents to hold the given number of blanks; and a constructor that takes values for height, width, and a character to use as the contents of the screen.
Giving the screen a default constructor was easy. The next part is probably easy aswell, I just dont understand what they mean when they say "and initalize the contents to hold the given number of blanks" and something in the 3rd part when they say "character to use as the contents of the screen".
Think I have made a breakthrough... Would the constructor for the second part look like this:
screen(pos ht, pos wd) : contents(ht*wd) {}
or something?
C/C++ :: Declare Parent Object Inside Class Constructor
Mar 24, 2014This keeps giving me the error
ecg.h:18:11: error: field "next" has incomplete type
How do I do what I need? It does the same thing whether I use a class or a struct. This is C++ code
struct ECG_node {
double voltage;
clock_t time;
ECG_node next;
[Code] .....
C++ :: Initializing Base Class Part From Derived Object Using Copy Constructor
Feb 20, 2012class Base
{
char * ptr;
public:
Base(){}
Base(char * str)
[code].....
Obj1 is a derived class object where base class char pointer is initialized with "singh" and derived class char pointer is initilized with "sunil". I want to create Obj2 out of Obj1. Separate memory should be created for Obj2 char pointer (base part and derived part as well) and that should be initialized with the strings contained in Obj1.
Here the problem is: Derived class part can be initialized with copy constructor. How to initialize the base class char poniter of Obj2 with the base class part of Obj1. char pointers in
both the classes are private.
I tried using initializer list but could not succeed.
Is there some proper way to do this?
C# :: Creating Instance Of A Class Given Its Assembly Object
Jan 15, 2015Let's say I reference a dll in my project that has an abstract class in it:
public abstract class Module {
public string type;
public abstract string doSomething();
}
And then I have an Assembly object, loaded from a dll that is not referenced in project, but rather loaded during run-time, containing:
public class Tester : Module
{
public static string type = "Test";
public override void doSomething() {
//Stuff being done
return "hello";
}
}
How can I get the value of "type" in the class that is loaded during runtime? How do I use the "doSomething" method of it and get the returned object?
C++ :: Derived Class Constructor Using Base Class Constructor?
Jan 1, 2013Is 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?
C++ :: How To Get Object Of Original Class From Function Of Other Class Where Other Class Object Is Member Of Original Class
Jan 21, 2013The case is like
class B{
public:
somedata;
somefunction();
}
class A{
public:
data;
function();
}
in somefunction i want a pointer to current object of class A m new to c++
C++ :: Creating Object Without Default Constructor
Jun 24, 2013I have a question about the default constructor.
To my best understanding, the compiler will provide me with a deafult constructor only if there are no any user defined constructors, at all. Now consider the following code:
Code: class MyClass
{
private:
int m_data;
public:
MyClass(int init):m_data(init){cout<<"Ctr called"<<endl;}
[Code] ....
How is it that suddenly, there is a default constructor?
C++ :: Initializing Inner-objects Of Base Class From Driven-class Constructor
Jan 6, 2015Let'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 .
C++ :: Invoking Base Class Constructor From Derived Class?
May 15, 2013I 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?
C++ :: Creating Array Of Pointers To Base Class To Point To Derived Class Objects Dynamically
Jan 16, 2013Please consider the following code :
#include <iostream>
using namespace std;
class superclass;
class subclass1;
class subclass2;
[Code] ....
As you can see I want to create a dynamically allocated storage of references to a parent class each of which can then point to a child class, how ever I do not know how to extract the child class out again from that array so i may access its variable b.
C++ :: Can One Constructor Of A Class Call Another Constructor Of The Same Class
Mar 19, 2015to 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).
C++ :: Transfer Values Set In Privates Of Base Class By Object Of One Derived Class To Another
Apr 26, 2014I have my main.cpp like this:
#include <iostream>
#include "curve1.h"
#include "curve2.h"
using namespace std;
int main() {
Curve1 curve1Obj;
Curve2 curve2Obj;
[Code]...
Base class Score has two derived classes Curve1 and Curve2. There are two curve() functions, one is in Curve1 and other in Curve2 classes. getSize() returns the value of iSize.
My base class header score.h looks like this:
#ifndef SCORE_H
#define SCORE_H
class Score {
private:
int *ipScore;
float fAverage;
int iSize;
[Code]...
You can see that I have used curve1Obj to enter scores, calculate average and output. So if I call getSize() function with cuve1Obj, it gives the right size that I took from user in enterScores() function. Also the result is same if I call getSize() in score.cpp definition file in any of the functions (obviously).
.....
The problem is when I call curve() function of Curve2 class in main (line 23) with the object curve2Obj, it creates a new set of ipScore, fAverage and iSize (i think?) with garbage values. So when I call getSize() in curve() definition in curve2.cpp, it outputs the garbage. .....
How can I cause it to return the old values that are set in curve1.cpp?
Here is my curve2.cpp
#include <iostream>
#include "curve2.h"
using namespace std;
void Curve2::curve() {
cout << "getSize() returns: " << getSize() << endl; // out comes the garbage
}
Can I use a function to simply put values from old to new variables? If yes then how?
C++ :: Using Member Function Of A Class In Another Class And Relate It To Object In Int Main
Aug 21, 2013I am writing a program which is using SDL library. I have two different classes which one of them is Timer Class and the other is EventHandling Class.
I need to use some member functions and variables of Timer in some Eventhandling Class member functions, Although I want to define an object of Timer in int main {} and relate it to its member function that has been used in Eventhandling member function in order that it becomes easier to handle it, I mean that I want to have for example two objects of timer and two objects of Eventhandling class for two different users.
I do not know how to relate an object of a class from int main{} to its member function which is being used in another class member function.
Lets have it as a sample code:
class Timer {
private:
int x;
public:
Timer();
get_X();
start_X();
[Code] ....
C++ :: How To Create A Class Object Inside Another Class
Feb 20, 2015My thought is that I would need to establish a variable for the class in the header and call the class within the .cpp file
//class A.h
B b;
Then in class A, to create the object and use a method from the object I would -
//class A.cpp
A::A(){
b();
}
int someAmethod(){
b.bmethod();
}
C++ :: Initializing Object Of Class Inside Another Class?
Mar 7, 2014I have a class MySeqBuildBlockModule that I am inheriting from: public SeqBuildBlock. Other than constructor and destructor, this class MySeqBuildBlockModule has a method: prep.
class MySeqBuildBlockModule: public SeqBuildBlock {
friend class SeqBuildBlockIRns;
public:
MySeqBuildBlockModule (SBBList* pSBBList0, long TI1_In, long TI2_In)// more arguements in this constructor of derived class
: SeqBuildBlock (pSBBList0)
[code]....
I would have like to intiantiate an object "myIRns_3" of a class defined in third party library
SeqBuildBlockIRns myIRns_3(pSBBList2);
and would like to access it from the prep function as:
double dEnergyAllSBBs_DK = myIRns_3.getEnergyPerRequest();
I tried to instantiate following in either private section or in constructor; but w/o any success:
SeqBuildBlockIRns myIRns_3(pSBBList2);
ERRORS encountered:
When I tried to do it inside the constructor, I get the following errors:
MySBBModule.h(113) : error C2065: 'myIRns_3' : undeclared identifier
MySBBModule.h(113) : error C2228: left of '.getEnergyPerRequest' must have class/struct/union type
MySBBModule.h(116) : error C2065: 'pSBBList' : undeclared identifier
MySBBModule.h(116) : error C2227: left of '->prepSBBAll' must point to class/struct/union
When I tried to do it in private section, I get the following errors:
MySBBModule.h(106) : error C2061: syntax error : identifier 'pSBBList2'
MySBBModule.h(113) : error C2228: left of '.getEnergyPerRequest' must have class/struct/union type
MySBBModule.h(116) : error C2065: 'pSBBList' : undeclared identifier
MySBBModule.h(116) : error C2227: left of '->prepSBBAll' must point to class/struct/union
C++ :: Declaring Object Of A Class In Another Class
Jul 14, 2014Information:
I'm using Code::Blocks v12.11.
(I'm using C++/SDL2, but I think that's of no relevance)
Problem:
I create a class named "CSprite" in a "Sprite.hpp"-file. I create a "Sprite.cpp"-file, which includes the "Sprite.hpp"-file. I define the methods of the class "CSprite" in the "Sprite.cpp"-file.
When I try to create an object of "CSprite" in the class named "CPlayer" in the file "Player.hpp" I get an error message. (<-- Looks complicated I know, the code example will be more usefull than this)
Error in the build messages:
C:UsersLinoDocuments1 Data LinoFreizeit1 ProgrammierenC++ & SDL2The Running ManCPlayer.h|30|error: 'CSprite' does not name a type|
||=== Build finished: 1 errors, 0 warnings (0 minutes, 1 seconds) ===|
Code Example:
Sprite.hpp
#ifndef _SPRITE_HPP_
#define _SPRITE_HPP_
class CSprite {
[Code] .....
What did I miss? Did I include the wrong file? Or did I Forget to include the file? Why do I get the error message?
I also tried it with a pointer declaration and the "->" Operator but I got the same error message. I know I could just write a new function to load the texture in my "CPlayer"-class but this would not really answer my question.
C++ :: Can Object Of A Class Be Assigned To Another Of Different Class?
Nov 9, 2013I fully understand that a variable of one simple data type cannot be assigned to another of a different data type in an assignment statement, except when type-conversion(i.e. casting) is employed. For structured data types (like classes), I know that the assignment operator can be overloaded; but this only addresses objects of the same type.
My problem is that I have read data from an input file into an object of one class, but I want to transfer the contents into an object of a different class in an assignment statement. Can this be realized given that the two operands of the assignment operator (=), in this case, would be of two different types?
C++ :: Importance Of Static Object In A Class And How They Are Different From General Object
Dec 13, 2012#include "B.h"
class A {
public :
A()
{
s_b = new B();
b = new B();
[Code] ....
In my project i have seen static object as above . But not able to know what is the exact use of it and how they are different from general object .
C++ :: Class With Enum And Constructor
May 29, 2013I 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?
C++ :: Class Course / Constructor Errors
Mar 22, 2014# 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.
C++ :: Can Use Class Constructor To Run Code In CPP By Itself?
Jan 13, 2015I 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.
C/C++ :: Add Copy Constructor To Class?
Nov 15, 2012This 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] ....
C++ :: How To Redefine A Constructor From Parent Class
Jul 14, 2014Firstly 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.
C++ :: Declare Class Member Outside Of Constructor?
Jun 27, 2013Basically, 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].....