C++ :: How To Access Class Member And Methods From Static Method (signal Handler)
Dec 4, 2014
I am writing my program on C++ language. I have one promblem. I need to set signal handler for my process. As the signal is related with the process on system level I have faced the problem.
My program consists several classes. They are connected together. But it doesn't metter in this case. The problem is that I need to access to member and methods of the class from my signal handler. For instance , I have class named Foo at it has some members and methods.
So from my handler I need to call its function and change members.
I understand that compiler should know that this class instances will exist during all program execution.
I have tried to set static member class Foo instance in another class , but this didn't solve the problem.
What is correct approach to do this. How to correctly implement signal handling in such case.
Here is example of my code
Code:
class MyContainer{
private:
std::vector<Foo> container;
public:
int removeFromContainer(Foo* aFoo) {
I need to set signal handler for my process. As the signal is related with the process on system level I have faced the problem. My program consists several classes. They are connected together. But it doesn't metter in this case. The problem is that I need to access to member and methods of the class from my signal handler. For instance , I have class named Foo at it has some members and methods.
So from my handler I need to call its function and change members. I understand that compiler should know that this class instances will exist during all program execution. I have tried to set static member class Foo instance in another class , but this didn't solve the problem. How to correctly implement signal handling in such case.
Here is example of my code
class MyContainer { private: std::vector<Foo> container; public: int removeFromContainer(Foo* aFoo) {
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?
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."
The problem occurs in here, I get access violations, is there a way to this while keeping Display const or is this code valid and my problem is somewhere else and not being caught in the debugger? I tried to make the return types const - but that didn't work .....
//Getters need const twice for this to work? const char* Player::GetName() const {return m_name;} const int Player::GetGrade() const {return m_grade;} const double Player::GetGPA() const {return m_gpa;}
Basically am trying to reference a method in a my Form1 class into another class. So far I have tried multiple different methods to try and access the method but have not managed it so far. Both classes use the same namespace. The part of my form class that I am using are as follows:
public class Form1 : Form { IContainer components = null; private ButtonPanelThread p1, p3, p4;
So I have an ImageManager class, Board class, and Box class. In Board.h I can declare ImageManager imgr; and in Board's constructor I can use imgr and its functions and such. However, in Box.h when I try and declare ImageManager imgr; I get the error "cannot access member declared in class ImageManager". Both declarations are under private, and exactly the same, but one doesn't work. Also, is there a way to only have one instance of ImageManager?
"You cannot initialize the static data member in the class definition — that’s simply a blueprint for an object and initializing values for members are not allowed. You don’t want to initialize it in a constructor, because you want to increment it every time the constructor is called so the count of the number of objects created is accumulated."
Why don't you want to initialize it in a constructor?
Edit: Because every time it is called it will set it back to 0 or whatever the initializing value.
For example, in a header file A.h, I define an abstract class,
Code:
// A.h class A { public: virtual void foo() = 0; private: static int _x; };
How'd I initialize static member data _x?Normally, we initialize a static member data in a cpp file. However, there is not cpp file for A.h. If I intialize _x in header file, there will be linker errors like mulitple defined symbols. What is appropriate way to do that?
I have a class having static member.I have get and set methods which will Get and Set Values to this variable. In a multithreaded application does it have any thread safety issues.
Class a { static int b; void Set (int c); int Get(); };
I've been trying for more than one month to access a method found in a library called libcocosnas_static.a. I'm using Cocos2d-X version 2.0.4. The library has been used many times by my company to make games using cocos2d-1.0.1-x-0.12.0 without any problem.
This is what I've done: 1- I added the include paths of the library to both eclipse and Android.mk 2- Included the .h file using #include "NASPlatformUtil.h" 3- Added the libcocosnas_static.a file to the proj.androidobjlocalarmeabi folder 4- Added "LOCAL_WHOLE_STATIC_LIBRARIES += cocosnas_static" to the Android.mk file 5- Called the function using: NASPlatformUtil:: openUrl("http://xxx.xxx.com/");
I can right click on the function, click Open Declaration and get it without any problem, but the compiler keeps on giving me that dreaded error...
This question is more from a design point-of-view rather than coding it to be a fully functional.
So here it goes:
I have multiple files which each require their own object of same class type (ref. First Class). File contents are read from a file to a unordered_map<std::string, std::vector<std::string>> which is either private or protected member inside First Class. First Class does not need any public functions to add, remove or change the data during runtime, but changes are only being made by checking if the file size has changed during the day, if the size is not equal to the last check, map gets updated.
Now, I have a Second Class which is a data handler class. It has public member functions with arguments that needs to be get from First Class's unordered_map using const_iterator. Which way to go with design and implementation.
I know there's two methods to do this. Re-doing handler class is also not out of the question. These two methods I'm aware of are:
1. Declare these maps to local scope, build few global functions and here we go. (Probably the easiest way.)
2. Create public member functions to a First Class which either return a pointer or a reference to a protected/private member. (I'm under the impression that I really shouldn't be doing this because of a bad coding practice.)
Note that I don't need any code here, just some other point-of-views regarding the subject itself for learning better coding practices.
Basically I want to create a base class which defines a static data member so that its automatically redeclared as the same static data member in the derived class.
class A{ protected: static derivable int val; // A::val }
class B : public A{ // static derivable int val is already here // A::val AND B::val }
This seems impossible to me but I'm wondering if perhaps there's a way to add modifiers to the compiler to do this (or preferably something MUCH simpler)...
Error10error C2248: 'std::thread::thread' : cannot access private member declared in class 'std::thread'c:program files (x86)microsoft visual studio 11.0vcincludexmemory06061ConsoleApplicationa
Suppose I make a class, something like having the constructor being invoked first makes sense, I don't have a problem with that. But, how could I limit access to functions until certain functions are called? Perhaps this isn't built into the language so you can't. And maybe this problem never comes up. For example if you have a set() and get() functions, if they are both public functions, there doesn't seem to be a way for the compiler at least now if set() never gets called you shouldn't call get(). I just see this as error prone if you need to use libraries, you have to know not to do it from documentation instead of something the compiler can check.
When I put boost::thread Thread; in my struct I get the error error C2248: 'boost::thread::thread' : cannot access private member declared in class 'boost::thread'
I have `MainShop`(base class) then `SwordShop` and `BowShop`(derived classes) and another derived class called `Inventory`. I have a vector under protected in my base class, and when I access it from my derived classes it's okay, but each one has its own value. How can I set them all to have the same value?
//MainShop.h #pragma once class MainShop { private: //some variables protected: vector <string> WeaponInventory;
[code]......
Here every time I run it, it goes straight to the `else` and it displays that I do not have any items. I want to just have one vector for both my bow and Sword shops because vectors take up a lot of memory and my teacher said keep them to a minimum. So I just want one vector that takes in items from my bow class as well as my sword class, but for some reason it's acting as if I have multiple vectors, each with its own set of items.
I am currently doing the assignment about linked list. Here are some details information about what I am doing.. This program is C++ and should run on Visual Studio 2010. And it contains three file, two datastructure header and one main cpp file.
This program is trying to arrange and show some sports records. The main program which contain the functions such as reading the result text file(each result text file contain several records of athletes), removing a file, arranging the totalresult and printing it out. And the main program is already given and I cannot overwrite it.
But when I finished and try to build the solution and run it, I am not able to run the program and it give me somethings like these...
warning C4172: returning address of local variable or temporary error C2248: 'Datastructure1::Datastructure1' : cannot access private member declared in class 'Datastructure1' see declaration of 'Datastructure1::Datastructure1' see declaration of 'Datastructure1' This diagnostic occurred in the compiler generated function 'Result::Result(const Result &)'
And I have tried to comment each function part of the header file and see if can run or not. But I still fail to do so. Here are my codes...
#ifndef DATASTRUCTURE1_H #define DATASTRUCTURE1_H class Datastructure1 { Public: Datastructure1( );
[Code] ....
There are two header files and look quite long. They are all some linked list functions . I have read and learn linked list data structure before I complete this programs. However, when I complete the functions required, the function cannot be compile....
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?
