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Hy, my question is simple..
I have this function.
CPythonMessenger::CPythonMessenger(): m_poMessengerHandler(NULL)
{
}
What scope have and why is there since constructor is empty and also is not used m_poMessengerHandler(NULL) i want to say the function is not used anywhere is constructor.
I guess you are examining (or maybe it is your code) THIS.
CPythonMessenger is the default constructor for the class CPythonMessenger as you can see in the relative header file HERE. After the : you can invoke a method (or another constructor) that must be run when creating an object of CPythonMessenger type. In particular, it creates an instance of m_poMessengerHandler that is then used in several place in the other class methods.
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For example, I have my class employee. I want to keep record how many employees till date have worked for me. I can make static count variable and add 1 in my constructor. But whenever my temporary object will be created when we pass object in parameters or return object of our class it will add for them too.
Static class member is the right way to go. A few things to be careful about:
Make sure you overload all constructors. The ones you don't want to support you should explicitly delete.
Don't forget to decrement in destructor.
If this program of yours is multithreaded then use atomic_uint or provide locking mechanism of your own.
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I know that we can directly assign same class objects in C++,but what actually happen behind the scene?
There's something called "default copy-constructor" and "default assignment-operator". Unless you overload these methods in the class, the default behavior is that all non-static members of the class are copied one-by-one from the source to the target class.
A little more: This includes pointers, btw. Which is why you generally should overload these operators and follow the rule of three if you have pointers as members.
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Please provide a simple solution to restrict inheritance in C++.
Yes! As of C++11, there's a final specifier you can use to indicate that a class cannot be inherited from:
class DontInheritMe final {
// This class cannot be inherited from.
};
If you have experience in Java, the final keyword in C++ in this case works the same was as final classes in Java.
If u really dont want to inherit a class,then just make its member variables and member functions as private ,if other class tries to inherit it they cant have access to its funtions and variables anyways.
But using final is a better option
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A simple example of how you would structure this would be particularly useful.
This is how I would do it:
MyMotor is an instance of the class Motor. This class has four functions idle(), accelerate(), flat(), decelerate(). (I assume you know how to build a basic class with private members and its constructors)
Then in main(), I create MyMotor and control it based on states. States can be controlled/monitored using Boolean Values. Whatever state I am in and whenever, certain function will be called.
Next time give it a try before you ask here, in order to get better responses.
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Any ideas why I keep getting this error?
http://codepad.org/jPQzMWvG
You declared a destructor in the header (line 36), but you haven't defined it in the source code. Add this to the source code, and you should be fine :
Entity::~Entity()
{
// do the cleanup here
}
Your class definition includes a destructor ~Entity but there's no implementation for it in the Entity.cpp file.
You've declared a destructor ~Entity() (and also ~Block()), but not implemented them anywhere. If the destructors are necessary, then implement them; otherwise, remove the declarations.
By the way, you should post the code in the question rather than an external website.