C++ :: Class Constructor With String Const Pointer As Parameter
Feb 19, 2013I know my product.cpp constructor is wrong but how can I set my private variables.
//PRODUCT.h
#ifndef PROJECT1_PRODUCT_H
#define PROJECT1_PRODUCT_H
[Code].....
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C++ :: Calling Custom Constructor Of Element In Array Whose Class Has Const Members?
Apr 15, 2013If I have an array of some class, and that class has const members, is there some way I can call a custom constructor on elements of the array?
I can't seem to reinitialize an element in foos in the example below. A thread on stack overflow mentioned the copy constructor show allow it, but I get "no match for call to '(Foo) (Foo&)'" when I try it.
Code:
class Foo {
public:
Foo();
Foo(int x, int y);
[Code] .....
C++ :: Initializing Const Char Member Variable In Constructor?
Jan 23, 2015I have a class that defines a window (a popup dialog of sorts), and I want the name of that window to be constant. The only problem is that the name of the popup needs to match the title of the parent window, and I get the name of the parent in the constructor. So how do I go about defining this member variable to be constant and initializing it with a value in the constructor?
I want to do something like this, but I know this isn't allowed:
/* class.h */
class foo {
public:
foo(*parentWindowPtr);
[Code] .....
I should mention that yes the name of the parent window is const char *, and I would like to keep it this way.
C++ :: Calling Constructor From Constructor Set Pointer To Null
Jan 25, 2014VS 2012 / Windows 7 64 bit
class
class myclass {
public:
myclass(){/*stuff here*/}
myclass(int* p) {MyPointer = p; myclass()}
[Code] ....
it works until the myclass(int* p) calls myclass()
then the MyPointer will become CCCCCCCC (NULL value)!
is there a way to stop the second constructor from resetting the pointer value to null?
C++ :: Linked List Node Passed As Parameter / Argument Pointer To Pointer Notation
Jan 17, 2014I was having problems changing the value of my head node I passed it as an argument as head which would be the address. The parameter was defined as struct node *head. like this
bool deleteNode(struct node *head, struct node *delptr)
I tried manipultaing pointer values to change head node value but it did not work. I saw some code online which used pointer to pointers(in code below) to change head node value it worked I dont fully understand why. Would like better understanding of why.
Would also like to know why the argument call needed &head instead of just head.
remove = deleteNode(&head,found); opposed to remove = deleteNode(head,found);
#include "stdafx.h"
#include<iostream>
struct node{
[Code].....
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/C++ :: Const Pointer Pass By Reference In Print Function
Apr 21, 2014I am trying use a print function to print out data in a struct. My questions are:
1. I have to use pass by reference. For the print function, I am passing the struct pointer as a reference, however, I don't want the print function to accidentally change anything. How can I make it use const to ensure that?
2. The deleteprt function doesn't look right to me. I feel like it should just be delete ptr not delete [] ptr.
#include <iostream>
#include <fstream>
#include <iomanip>
#include <cstdlib>
#include <string>
using namespace std;
struct Inventory {
[Code] .....
C++ :: Variable Declaration (const Pointer To SensorBase Object)?
Feb 19, 2015I'm having to do a little c++ (coming from java) and don't understand the syntax of the following declaration
Code:
SensorBase* const sensor(mSensors[i]);
It looks like it's declaring a const pointer to a SensorBase object but I don't understand how that applies to sensor(mSensors[i]) which looks like a function??
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++ :: Static Const Class Instances?
Jun 17, 2012i have this rather large class, which (in a way) somehow resembles a custom dialog control). This control is supposed to display data, which it does just fine. To do so, it maintains a
byte settings[10];
array, which holds information on how to display the data.
There are multiple ways to represent this custom set of data.In order to remain flexible in representing it, i thought of implementing some sort of DisplayProvider, which can be registered to the base class and provides that settings byte array.
Preferably, i would now have a set of static const instances of this provider.Using a struct would work nicely here:
PHP Code:
struct DisplayProvider
{
int settings[10];
}
static const DisplayProvider prov1 = {1,2,3,4,5,6,7,8,9,0};
The problem: The DisplayProvider would have to do some pre-processing, before handing over control to the base class, which then does the main work.I would end up with something like this:
PHP Code:
class DispalyProvider
{
baseclass* owner;
int settings[10];
void PreProcessing(...);//ends up calling the owner.Processing(...) function
};
The main thing here is, that i dont really see a way to create a stock of default "static const DisplayProvder = {...}"s, as i could when using a struct.
C++ :: String To Const Char Error
Jan 15, 2013I'm currently finishing up an assignment that was half written by my professor. Below in the testGrades section of code there are two errors both are the same message.
Error: no matching function for call to Grades:: Grades(const char [15])
Test Grades
//Purpose: Test program for the class Grades
// Create stu1 Grades object
// Add 5 grades to stu1 - only 3 can be stored in stu1 - other 2 discarded
// Create stu2 Grades object
// Add only 2 grades
#include <iostream>
#include <string>
#include <iomanip>
#include "Grades.h"
using namespace std;
[Code] .....
C++ :: Const Static Members In A Template Class?
Jan 17, 2013I have a little problem with template classes and their specialization. Here is a short example:
template <typename T>
struct A{
// some typedefs
[Code]....
The above example is not compiling, because of the assignment of the const static double. Double needs a constructor, but that doesn't work (or seems not to work) with static.
I'm not sure, if it works at all in C++ that way. All I want is a template struct with some typedefs and a constant which is different for different specializations. Don't think it has to be static, but that would be better style, wouldn't it?
C++ :: Calling Derived Class Functions In A Function With Parameter Of Base Class
Mar 30, 2013Say I have 3 classes:
class Player {
public:
virtual func1();
[code]....
Say in my main class, I have a function fight(Player p1, Player p2) and I would like to do something like this in the fight function, given that p1 is the human and p2 is the computer:
//function fight()
fight(Player p1, Player p2) {
p1.func2();
}
//using function fight()
fight(human, computer);
When I compile the program, I got this: error: ‘class Player’ has no member named 'func2()' What can I do to allow p1 to call func2 inside fight()? I'm not allowed to use pointers as the parameter for fight() and have to use the signature fight(Player p1, Player p2).
C++ :: Void Pointer As A Parameter
Mar 14, 2013I want to have a function that has a pointer to an int/double/string so I thought I'd use a void pointer like so:
int someFnc(int a, int b, const void *key){
// take care of converting key into appropriate type in here
}
And when I want to use this function I'd like to be able to do something like this:
main{
...
int myKey;
someFnc(1,2,myKey);
]
But I get a compiler error telling me:
invalid conversion from 'int' to 'const void' -[fpermissive]
Do I need to convert myKey into a void pointer before passing it as an argument?
Why does passing myKey like this work?
someFnc(1,2,&myKey);
C++ :: Pointer As Parameter Is Null?
Apr 9, 2014In my raytracer-project I have the following function:
bool hitObjects(Ray &ray, std::vector<Object *> &objects, Vector3& normal, Material *mat) {
double tmin = K_HUGE_VALUE;
double t;
[Code]....
When I try to run this, I only get the message "Material pointer is null". So, somehow the pointer is null after the hitObjects-function is called, even though it isn't inside that function.
C++ :: Store Reference To Const Object In Class As A Member Variable?
May 27, 2014i want to store reference to a const object in my class as a member variable, as follow:
I basically want a readonly reference to |Data| in Device object.
Code:
class Device {
Device(const QList<QSharedPointer<Data>> & dataList) : _listRef(dataList) {
} protected:
const QList<QSharedPointer<Data>> & _listRef;
}
This does not allow me to initialize _listRef as something like NULL when it is not applicable.Also, i must change all my constructors and its child class to include an initialization of _listRef!!
What is the alternative? Is pointer the nearest? which of the following should be used?
Code:
const QList<QSharedPointer<Data>> * _listRef;
or
const QList<QSharedPointer<Data>> *const _listRef;
or
const QSharedPointer<QList<QSharedPointer<Data>>> _listRef; ????
C++ :: Initializing Const Struct When Data Is A String Literal
Feb 23, 2015I have a struct like this:
Code:
struct String{
char* data;
std::size_t size;
};
I would like to be able to create const variables of this type for string literals.
Code:
const String message;
Is there an elegant way to create a const String like this when data is a string literal?
I tried this:
Code:
const char *string_data = "Hello";
size_t string_size = strlen(string_data) + 1;
const String string = {string_data, string_size};
The problem with that is that string.data isn't considered const during the initialization of the String struct so the compiler throws an error. It doesn't feel very elegant to do it like this either way.
Is there an elegant solution to this problem? I would like to avoid making a copy of the string literal.
C++ :: Using Child Class As Parameter Of A Function In Its Parent Class
Aug 27, 2014I am currently having an issue with a piece of code that I am writing in which I need to use a vector of a child class as a parameter in a function in the parent class. Below is an example of my code:
#include "child.h"
#include <vector>
class parent {
parent();
function(std::vector<child> children);
// rest of class here
}
When I do this my program doesn't compile. However if I try to forward declare, as shown in the following example, it once again refuses to compile:
#include <vector>
class child;
class parent{
parent();
function(std::vector<child> children);
// rest of class here
}
This time, it refuses to compile because it needs to know the full size of the class child in order to create the vector. How to being able to access the child is essential for my program, so what should I do?
C++ :: Function Pointer With Object As Parameter?
May 30, 2013I'm making a code that uses a Function pointer. The problem is, when I try to compile appears an error like:
error: no matching function for call to 'rnVector::rnVector()'
Here's part of the code:
phiFunction::phiFunction(double (*f)(rnVector), rnVector (*df)(rnVector)) {
//... Here comes the code stuff...
}
C++ :: Cast Base Class Pointer To Derived Class Pointer
Feb 6, 2015I create an instance of a base class (not derived class) and assign it to base class pointer. Then, I convert it to a pointer to a derived class and call methods on it.
why does it work, if there is a virtual table?
when will it fail?
// TestCastWin.cpp : Defines the entry point for the console application.//
#include "stdafx.h"
#include <iostream>
class B
{
public:
B(double x, double y) : x_(x), y_(y) {}
double x() const { return x_; }
[Code] ....
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++ :: How To Use Function With Pointer Parameter To Print Array
Jul 20, 2013The printArray function should take in the dynamically created array and the size of the array as parameters. It should print out the contents of the array.
#include <iostream>
#include <string>
using namespace std;
[Code].....
My problem is that how to write the code to print the array using pointers. I've been stuck for awhile trying to figure it out.
C++ :: How To Pass Function Pointer As A Template Parameter
Jun 13, 2013void extf(int a) { }
template<typename P>
struct A {
// 1
template< void (*F)(P) >
static void call(P arg) {
[Code]...
Why it is not working? What would be a proper way to pass function pointer as a template parameter?
C++ :: Copy Constructor Containing Pointer?
Nov 24, 2014I want to copy over values from x to y, and its not possible as i cant use "y" as a index in my pointer array.
Code:
CellularPhoneStock::CellularPhoneStock(CellularPhoneStock &origObj){
this->phonez[nrOfPhones]->setColour = origObj.getColour();
/*this->model = origObj.model;
this->nrOfType = origObj.nrOfType;
this->price = origObj.price;*/
nrOfPhones++;
}
My questions is, how can I use origObj and phonez combined to use the function getColour() ?
Btw, phones = CellularPhone * phonez[30];
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++ :: Using Constructor Within Constructor In Same Class
Feb 28, 2012I 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] ......