C++ :: When To Use Static Classes
May 2, 2013
I am just wondering what the best practice is for when to use static classes (by static class, I mean a class which has only static attributes and functions).
If you are creating more than one independent object of a particular class, then obviously this should not be static because each object will be the same. But what about the case when you know that you will only ever need one instance of a class? On its own, does this mean that you should create it as a static class?
Personally, I use static class when I want its member attributes and functions to be available globally, which I think is fine. However, I am not sure about the case when I know that only one object will be created - should this be a static class or not?
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Mar 1, 2013
If I have a static variable in a class e.g. a pointer to another class like this: (B is another class)
class A {
public:
static B* cB;
};
Then I set that variable and create multiple instances of class A like this:
A::cB = new B;
As = new A[Number];
Then will the value of cB be the same across all instances?
I cannot pass the class pointer in the constructor as I need to create an array of instances. I tried this method but I get linker error.... unresolved external.
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Jan 9, 2014
so i was trying to find out how to do unbuffered input in linux and came across this class: [URL] . i didnt like how i had to create a new instance of it each time i wanted to use it, so i made the functions static and renamed the class to Buffer. i could then call it like this: Buffer::On(); Buffer::Off();. My question is, when doing something like that where the class consists of two functions that can exist indepently of another, which is better: a class like what i did or wrapping it in a namespace?
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Oct 15, 2013
I wanted to ask if it is somehow possible to do:
Code:
class RaspberryPi: public Singleton<RaspberryPi> {
private:
static const DeviceInfo GPS;
template<typename Register_t>
auto ReadGPS(Register_t& Register) -> void
[Code] ....
There are two limitations I am facing:
First, it seems that anything that is part of a struct cannot be a compile-time expression. It's a nice way to group information, so it would be nice to have.
Secondly, it seems that all compile-time expressions cannot be inside a class (at least according to VC++), which means I have to move them to global level, but while it can be done, I don't really want to do it, because it's a platform detail.
In this case, static type dispatch would be nice to have because I have a function
Code:
template<typename Register_t>
auto ReadBus(Platforms::DeviceInfo Device, Register_t& Register) -> void {
switch (Device.Bus)
[Code] .....
There are two types of registers. With runtime dispatch, I get disgusting errors such as "could not deduce template arguments, blah blah" if some object doesn't have the required interface (i.e., don't have overloads for both register types). So the workaround would be to add two overloads and use something like asserts to stop invalid code from running, but it would be so nice to only allow correct code to compile and not get scary error messages.
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Apr 17, 2013
From my book:
"A static function might have this prototype:
static void Afunction(int n);
A static function can be called in relation to a particular object by a statement such as the following:
aBox.Afunction(10);
The function has no access to the non-static members of aBox. The same function could also be called without reference to an object. In this case, the statement would be:
CBox::Afunction(10);
where CBox is the class name. Using the class name and the scope resolution operator tells the compiler to which class Afunction() belongs."
Why exactly cant Afunction access non-static members?
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Sep 11, 2013
What are the workarounds for accessing the non-static member variables of some class(Say A) inside static member functions of another class(Say B)? I am coding in c++. Class A is derived with public properties of class B. Any pointers?
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Aug 22, 2014
Have following code:
class Program
{
static void Main(string[] args)
{
[Code]....
My question according to what i just wrote:
1. Is that mean that Do() is only available for use by Dog itself because Dog is 'oryginal' Dog, and if i create new dogs - instances of oryginal Dog (dog1, dog2 ...) they cant access because Do is only available fo 'oryginal' one? Is that correct thinking?
2. If i would want to have something common (e.g value) for all dogs is that good way to create static field/method for Dog instead of non-static once then all instances of Dog would access Dog static member to get/change it? Just stupid example: static method GetAmountOfLegs() which return 4 Then all instances can take/call that value from Dog. Is that correct thinking?
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Oct 5, 2013
I have an array of (Student)classes created in Manager.h, which contains a new instance of class Name (name),(in Student.h)How would I go about accessing the SetFirstName method in Name.cpp if I was in a class Manager.cpp? I have tried using Students[i].name.SetFirstName("name");
// In Manager.h
#include"Student.h"
class Manager
{
[Code]....
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Aug 5, 2013
Here is the code,
Code:
class A {
};
A& CreateObject() {
static A a;
return a;
} static A aa;
int main() {
return 0;
}
So is there any difference between a defined in CreateObject and aa?
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Aug 26, 2013
I want to know that how objects of two different classes interact with each other???
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Aug 13, 2014
In this program the intention is to create a menu driven program for a pizza restaurant. I have to use a class called Pizza and have to include at least three public functions; one is called SetSize, another one is called Display, and the last one is called ComputePrice. A small pizza is worth $10, a medium is $14, and a large is $17. Each topping is worth 2 dollars. I know that the program runs correctly, but I have doubts over the classes and function actually being utilized correctly or at all.
Program:
#include <iostream>
#include <iomanip>
#include <cmath>
using namespace std;
class Pizza {
private:
int size;
int style;
[Code] .....
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Oct 23, 2013
I'm trying to use multiset with a user defined class "edge". I'm trying to use the multiset as a priority queue, and I've created a "less<edge>" via operator<() overloading.
For some reason, I cannot insert edges into the multiset.
I understand that I might also have to create an "allocator". I got some ideas for creating it at [URL], but still don't know how to define size_type and difference_type.
Attached is my skeleton code, running on Windows 7 (32-bit), under Netbeans IDE, using Cygwin g++ 4.7.3.
How can I get this to work? What is important is that I get a priority queue working with my edges, prioritized by the weight.
#include <iostream>
#include <set> // for multiset
using namespace std; // assume std libraries (i.e. std::XXX)
class edge { // node, weight pair
public:
[Code].....
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Oct 14, 2013
So, even though the virtual pointer is constant across objects of class why cant it be made as static. Why each derived instance is having the pointer to vtable.
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May 5, 2013
I've created a base DLL for all my future DLL's, a way of getting version numbers and such and that compiles fine, but I can't add it into a class for a new DLL. All the headers do have an appropriate cpp to define the function declarations (and they compile fine).
All for the base DLL I have:
LibVer.h
Version.cpp
Function.cpp
LibVer.h
#pragma once
#include <vector>
#define DLLEXPORT 1
#define DLLIMPORT 2
#define DLL DLLIMPORT
[Code] .....
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Jun 19, 2014
I have a class where I'm trying to create two static maps. I know I haven't separated the implementation from the declaration. This is how I'm required to program at the moment.
My example class that I'm trying to compile looks like this:
#include <map>
#include <string>
class Foo {
[Code]....
I keep getting compiler errors, though, saying:
invalid use of qualified-name Foo::map1
and
invalid use of qualified-name Foo::map2
I can't initialize these maps explicitly; in my real program they're created by reading in a few different files' data on startup. I need to be able to access the maps throughout my entire application, and I don't want to be required to read in the same data file over and over again.
how static maps can be created properly, or failing that explain another methodology I could use to make them available to my entire application?
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Jul 1, 2014
I have the following scenario: I plan to have an xml configuration file.I have a trader that lunch few strategies, each have different configurations. I plan to have all configuration reside in the same file as different nodes.
Now I want that each strategy will hard code the name of node it will loop up for its parameters. Since those paramters are requered for the init and I use DI (configuration are passed in the constructor) I want to make it static.
So this would be something like.
public class Strategy: Base_strategy{
public const string _conf_name = "XXX";
public static string get_conf_name(){
[Code]....
Since other people will code strategies, I want each strategy to implement this static function. I wanted to do this in an interface so that anyone coding new strategy,implementing the base strategy will have to code this static function as part of the contract.
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Feb 23, 2014
im creating an address book. One address book contains a ListBox, New User button, Edit User and Remove User button. The first form is suppose to allow you to view the users you've created on the ListBox and you can decide whether you want to remove it, create a new one or simply edit the user. Now The second form simply contains labels and textbox along with a save button. I'm having a bit of issue figuring out the ListBox. I want to be able to create a user and have the user be posted on the ListBox. I read that i must instantiate listbox then simply add it. Now on my form2 i have a for loop that loops through an Array of String were all the users will be created on. How can i call that array of string on to the form1?
Form 1:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
[code].....
EDIT:I just figured out that to call a variable from one form to another you simply instantiate the form then simply call it. PS. must be set to public:
ListBox1 createUser = new ListBox1();
createUser.userString[0];
why doesnt it show the windows when i run without debugging?
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Feb 22, 2015
n the requirements it says this;
-create a get and set for height, width, length.
-A default parameterized constructor = 1
-A method to resize the box
-A method to get the volume of the box
-A method to convert the object to a string
My Questions:
The 3 parts I am confused by are the default parameter constructor, the re-size the box and the method to convert to string. For the default parameter part I figured making length, width and height = to 1 would work, but I'm pretty sure thats not what I'm supposed to do.
This is the main file
#include "box_class.h"
#include <iostream>
using namespace std;
int main() {
double length;
double width;
double height;
double volume;
[Code] ......
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Jan 24, 2012
I'm trying to make a template class which holds a template list I made. The list consists of template nodes (another template class I made).
My problem is that in some places (not everywhere) the compiler says that I'm trying to access private members of the node's class.
For example, if I define my node like this:
template<class T>
class CoefNode {
private:
T coef;
[Code]....
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Mar 12, 2014
I'm working on a project involving nested classes and structs like this:
Code: class A {
public:class B {
public:f()
{A::C* iCanDoThis; //no errors.
iCanAlsoDoThis->root->.... //this also works fine.}private:A::C* iCannotDoThis //this is what I would like to do.
Has errors
A* iCanAlsoDoThis;};private:struct C
{..data..};
C* root;};
Is it possible make a pointer to struct C a private member of class B?
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Mar 6, 2015
I have a hpp file with a list of inline finctions like this:
Code:
inline int check() {
return 1;
}
inline int check_1() {
return 1;
}
... What I would like to do is to include them into several unrelated classes. How can I do this. Can I just add the hpp inline functions in headers of my class containing files or not. I mean if they are not defined as class functions how can they be called. I don't understan the logic.
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Mar 6, 2015
Is there a way to export a c++ class for another language. I need to find an interpreted language that can use c++ classes (actually just one class) exported in DLLs. It wouldn't surprise me if you couldn't though because of how classes are handled in c++. Maybe python could do it because it's object oriented uses something very similar to the "this" pointer.
I have heard about something called COM.
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Jan 6, 2014
I have the codes for the functions: "Given the functions that we have discussed and defined in the class and the code that we have created, create the code for the Delete Node function and the Search function. Create an application that will incorporate all the functions that we have discussed and the new ones that you need to create. The application should allow the linked list to be built initially from a text file. The application should then allow for the user select an operation to perform. The acceptable operations are
- to search for an item
- to delete an item
- to enter a new item
- to exit the application
After the initial build and loading of data from the textfile, the application should print a listing of each item in the list and the node that it is located in. after a delete or insert, the application should display an output of the list again showing each item in the list and the node that it resides in.
The data item for this problem will be the inventory structure that we created in class and the data is in the inventory file that you already have downloaded."
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Dec 27, 2013
I was exploring static variable by writing code snippets. I tried below code and it ended up throwing error saying "error: storage class specified for parameter 'b'"
Why static cannot be used in func() ?
Code:
int main() {
int a;
a=5;
func(a);
printf("%d",a);
return 0; }
void func(static int b)
{b=6;
printf("%d",b); }
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Oct 7, 2014
I am trying to refresh my memory here as I did some studies many years ago but the results elude me.Also todays c/c++ compilers may have better optimizations.Say I have a static library that includes three obj modules.Each of these object modules has a number of functions. These functions do not reference any other functions within the obj module.My main app links this library but only references one function from each of the object modules.
Question: Are the complete contents of each module linked into my main app or are todays linkers smart enough to just link the functions used?
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Oct 8, 2013
I've written a doubly linked list per my assignment instructions. I've implemented begin() and end() iterators for it, and they work with no problems when traversing the list. However, I need to sort the elements in the list. We are allowed to use the sort function defined in the <algorithm> header since we haven't yet covered sorting algorithms.
But, I'm running into a ton of problems. I figured as long as the begin() and end() iterators were defined for the list, then sort(list.begin(), list.end(), compare) would do the trick. The main errors I'm getting are:
error: no type named iterator_category
error: no type named value_type
error: no type named difference_type
error: no type named pointer
error: no type named reference
And also errors for no match of the + and - operators for the iterator class.
I understand reference, pointer, and value_type, but I have no idea about iterator_category and difference_type. Additionally, I'm a little unsure why the + and - operators need to be overloaded.
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