The * in C++ Initialisations
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The Definitive C++ Book Guide and List
I'm new to C++ and have been playing around witha few examples, I was just wondering what the * meant when initialising a class.
Normally in AS3 I would do this:
MyClass myClass = new MyClass
But I have seen this in c++
MyClass *myClass = new MyClass
What is the star for, I;ve seen it used sometimes and not others.
Thanks!
The asterisk in C++ means many things depending on its place in the program. In this specific instance, it modifies the meaning of myClass to be a pointer to an instance of MyClass , rather than an instance of MyClass .
The difference between the two is that the lifetime of an instance ends when it goes out of scope, while an instance that you allocate and reference through a pointer remains valid even after a pointer goes out of scope.
It is valid to have a declaration like this:
MyClass myClass; // no "new"
In this case, it is not necessary to use new , but the instance's life time is tied to the scope of the variable myClass .
It's called a pointer. If you're using a C++11 compatible compiler, you can do the following:
auto myClass = std::make_shared<MyClass>();
If you were using a "raw" pointer, you would need to manually delete it when you are finished with the memory, with the shared_ptr , this isn't necessary.
An asterisk stand for a pointer . A pointer is a memory adress. When you write MyClass *myClass , you create a pointer to the beginning of the bits range where your new MyClass is created.
Creating an object with new , you become responsible of it life cycle. YOU will need to delete it when you dont need them anymore, whereas creating MyClass myClass; will be destroy when exiting the scope where you create it. You still can access myClass memory adress even when written this way, using & operator.
If you need more explaination, try to get one of those books.
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