C++ :: How To Use A String To Create Class Object

Dec 24, 2014

I wanted to create a new class object and I want to name it from a string. Something like this:

string name = "Mike";
Customers name;
//to create a new object in customer class using the name string

Is there any way to do this?

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C++ :: How To Create A Class Object Inside Another Class

Feb 20, 2015

My 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();
}

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C++ :: Create 5 Instance Object Of Class Test?

Apr 27, 2014

I am new to C++. I am trying to create 5 instance object of class Test. I wonder if these two codes are the same.

Test testArray[5];
//which one is the correct way or what is the correct way?
for(i=0;i<5;i++)
{
Test testArray;
}

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C++ ::  How To Create Global Object / Instance Of A Class

Aug 25, 2013

I'm new in object oriented programming. I need creating a global object/instance of a class, that can be used by any function.

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C++ :: How To Get Object Of Original Class From Function Of Other Class Where Other Class Object Is Member Of Original Class

Jan 21, 2013

The 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++

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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 .

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C :: How To Create An Object

Oct 31, 2013

I have an assignment that asks me to implement a variant of the classic bouncing balls program.

'Each ball should start off at the top of the screen with a random speed in the x direction. Whenever a ball hits a screen boundary it should bounce off at an angle equal to the impact angle and lose some speed. Eventually each ball should come to a rest at the bottom of the screen. Five seconds after coming to a rest a ball should be removed from the screen.'

'Your code must keep track of objects (balls) by placing the object data structures in a linked list. You need to create your own linked list implementation. Below is a brief description of the object programming interface: CreateObject - Create a new object. The function accepts as input parameters a pointer to the SDL screen, a pointer to a model triangle array, and a variable telling the size of the model triangle array. The function returns a pointer to a new object data structure. The model triangle array specified as input parameter should not be shared across objects. (Not sharing the model triangle array allows e.g. objects to have different colors.)

Perform the necessary memory allocation and copying.DestroyObject - Free object. The function accepts as input parameters a pointer to an object data structure. The function should free all memory allocated to represent the object (memory allocated for the model triangle array and the object data structure itself).

Drawobject - Draw object on screen. The function accepts as input parameters a pointer to an object data structure. The function must draw the object on the screen by calling DrawTriangle on each of the model triangles. Remember to update scale, translation, etc., in each triangle data structure before invoking DrawTriangle.

Hint: Do not make the bouncing algorithm too complex. Bouncing a ball off a vertical or horizontal surface can be accomplished without resorting to calculating impact angles.'

The function I'm stuck at, is the first one - createobject.

My first aim is to get one ball on the screen.

Code:

// Create new object
object_t *CreateObject(SDL_Surface *screen, triangle_t *model, int numtriangles)
{
object_t *object = malloc(sizeof(object_t));
object->model = malloc(sizeof(sphere_model));
object->screen = SDL_Surface;
memcpy(*model, object->model, sizeof(object_t));
return object;
// Implement me
}

This is what I've done so far.

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C++ :: How To Create A Global Object

Jan 18, 2013

if (choice ==1){
Light *myobj = new Light();
}
FlipUpCommand switchUp(*myobj);

Error: `myobj' undeclared (first use this function)

How to solve this problem without changing the Light class.

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C++ :: How To Create Global Object

Jan 18, 2013

if (choice ==1){
Light *myobj = new Light();
}
FlipUpCommand switchUp(*myobj);

Error: `myobj' undeclared (first use this function)

How to solve this problem without changing the Light class.

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C++ :: Transfer Values Set In Privates Of Base Class By Object Of One Derived Class To Another

Apr 26, 2014

I 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?

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C++ :: Using Member Function Of A Class In Another Class And Relate It To Object In Int Main

Aug 21, 2013

I 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] ....

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C++ :: Create Object Of Unsigned Template?

Jul 17, 2014

template<class T>
void function ( T item )
{
unsigned T willThisWork; // <--
}

Visual Studio compiles it, but will it actually do what I want? I do know that T is is a signed integer, I just don't know what size of integer.

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C/C++ :: How To Create A Vector In Header File That CPP Object Can Use

Apr 25, 2015

I'm working on a grocery store inventory project. One part is to have a shopping cart, where customers can put in up to 20 items. Because there can be up to 20 shopping carts at one time, I want to use a vector inside the cart object to represent all the individual food items.

Here's my code,

Header:

#ifndef CART_H
#define CART_H
#include <vector>
class Cart {
public:
Cart();
Cart(std::vector< int >, std::vector< int >)

[Code] ....

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C++ :: Creating One Class Object In Constructor Of Another Class

Sep 20, 2013

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.

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C++ :: Initializing Object Of Class Inside Another Class?

Mar 7, 2014

I 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

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C++ :: How To Create A Function That Takes A File Object As A Reference Parameter

Feb 21, 2013

I have a school project in which need to create a function that takes a File Object as a Reference Parameter. Supposedly, it should allow me to read the first piece of data from others separated by a space from a file. The later be able to continue reading from the next piece of data.

I know how to set things up to read from the data file, such as using

Code:

#include <iostream> , and

Code:

ifstream inputFileName;
inputFile.open ("nameOfFile");

I also understand how to pass a variable by reference to a function. But I simply cannot put the two items together!

I tried using

Code:

void getFileInput (ifstream &); //parameter
getFileInput ("nameOfFile") // call
void getFileInput (ifstream &dataFileName)

In the function I used

Code:

ifstream inputFile;
inputFile.open (dataFileName);

I'm just not getting an understanding of this concept!

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C++ ::  Declaring Object Of A Class In Another Class

Jul 14, 2014

Information:
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.

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C++ :: Can Object Of A Class Be Assigned To Another Of Different Class?

Nov 9, 2013

I 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?

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C++ :: How To Use Object From Another Class

Dec 21, 2013

I have two classes one called Date and the other is University , Date class has two overloaded operators , ostream and istream to take in the data and print them out :

ostream & operator<<(ostream & out, Date & x) {
out<< x.month << "/" << x.day << "/" << x.year ;
return out;

[Code] ....

The University class has an object of type Date called establishDate and I must use this to print out the date along with the University name and location, here's University class :

University.h

class University {
public:
University (); // constructor
friend ostream & operator<<(ostream & out, University & x); // print the university data
friend istream & operator>>(istream & in, University & x); // to read university data

[Code] .....

so how do I use the establishDate object ?

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C++ :: Converting Object To Different Class

Jun 22, 2014

Sandy is of class Person, who converts to Muslim and takes on a new name Fatima, and has all the attributes of Sandy, with new Muslim attributes (e.g. religion == Islam, etc..). At this point, Sandy can be deleted, and Fatima, now of class Muslim will play Sandy's role henceforth. The problem is that due to her new address, all the people who knew Sandy does not know Fatima. Manually changing Sandy's address to Fatima's address for all those people who knew Sandy is clearly not an acceptable method. I looked through all the design patterns and cannot find one to solve this problem. how to improve the design? Here's my simplified code showing the problem:

#include <iostream>
#include <string>
#include <typeinfo>
class Person {
std::string name;
Person* bestFriend;

[Code]...

Output:

sandy = 0x32658, 6Person
Mary's best friend is Sandy.
fatima = 0x23fec0, 6Muslim
Mary's best friend is Sandy.

Of course, we want to have: Mary's best friend is Fatima,. with mary->getBestFriend()->getReligion() == Islam, etc... How to redesign the whole thing so that this is automated (assume there are thousands of people who know her)?

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C++ :: Not Declare Object For A Class?

Jul 15, 2013

is it possible to don't declare an object for a class and use the function of this class ? i saw a code use this but i cannot find it again .

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C++ :: Static Object Of Same Class

Jul 27, 2013

What is the purpose of having static object of the same class.

E.g.

class someObj{
public:
static someObj obj;
};

how the compiler treats this object

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C++ :: Calling Object Within A Class?

May 10, 2014

class abc {
public:
int i;
abc * foooo;
};

How do you call * foooo? Say I create:

abc a;
* foooo would have some values for int i.

To get int i of *foooo, I tried a.foooo.i, which doesn't work. How do you call it?

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C++ :: Pass Class Object By Reference

Jun 25, 2013

I am having trouble working with third party dll's, libs and header files. I am trying to call a function.here is the function that is suppose to be called.

bool COAuthSDK::GetRequestToken(CClientDetails &objClientDetails)

it has this info of what it needs :

Name IN/OUT Description
m_environment IN Optional. Possible values are SANDBOX (default) and LIVE.
m_strConsumerKey IN OAuth consumer key provided by E*TRADE
m_strConsumerSecret IN OAuth consumer secret provided by E*TRADE
m_strToken OUT Returned by the function if successful
m_strTokenSecret OUT Returned by the function if successful
m_strCallback IN Optional; default value is "oob"

here is the COAuthSDK header

#ifndef _OAUTHSDK_H_INCLUDED_
#define _OAUTHSDK_H_INCLUDED_
#include "ETCOMMONCommonDefs.h"
#include "ETCOMMONOAuthHelper.h"
using namespace std;

[code].....

when I try to build the function it says that its in the dll's so I know I have to call it.here is the link to the build site if needed URL....

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C++ :: Size Of Object Of Class Child?

Feb 5, 2014

hiclass Parent {
};
class Child : virtual public Parent {
};

What is the size of object of Class Child in following case?

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C++ :: Pointer Class Object Vectors

Aug 4, 2013

#include <iostream>
#include <vector>
#include <string>
#include <map>
using namespace std;
struct bop {
string realname; //real name

[Code] ....

Okay, so first thing's first. The program will not compile due to lines 39-45. If I were to change those pointers into regular objects, it will not change the values of my class object. So what is the right way to do this?

I want the user to be able to input the # of employers/programmers into the system. But I cannot do that with an array of classes because when declaring an array; the array size must be constant.

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