Comma operator to the rescue! An expression (a, b) will evaluate a first, then b. class DisplayOpenGL { public: DisplayOpenGL(HWND hwnd) : m_device(hwnd), m_opengl((m_device.SetPixelFormat(), m_device)) { }; private: DeviceContext m_device; OpenGLContext m_opengl; };
Initialising any member with () performs value initialisation. Initialising any class type with a default constructor with {} performs value initialisation. Initialising any other aggregate type (including arrays) with {} performs list initialisation, and is equivalent to initialising each of the aggregate’s members with {}. Initialising any reference type with {} constructs a temporary object, … Read more
I wish to initialize bar to NULL. Is this the best way to do it? It is the correct way. So, yes. Also, is it necessary that the destructor is virtual? No. The destructor only needs to be virtual if you will be inheriting from the Foo class and will be using a Foo pointer … Read more
Yes, your use of member function in initialization list is valid and complies with the standard. Data members are initialized in the order of their declaration (and that’s the reason why they should appear in the initialization list in the order of their declaration – the rule that you followed in your example). N_ is … Read more
There are many ways to get there. Here are some of them (in no particular order of presence). Use vector(size_type n, const T& t) constructor. It initializes vector with n copies of t. For example: #include <vector> struct MyInt { int value; MyInt (int value) : value (value) {} }; struct MyStuff { std::vector<MyInt> values; … Read more
This is well-defined and portable,1 but it’s potentially error-prone. Members are initialized in the order they’re declared in the class body, not the order they’re listed in the initialization list. So if you change the class body, this code may silently fail (although many compilers will spot this and emit a warning). 1. From [class.base.init] … Read more
My question: is this std::move really needed? My point is that compiler sees that this p_name is not used in the body of constructor, so, maybe, there is some rule to use move semantics for it by default? In general, when you want to turn an lvalue to an rvalue, then yes, you need a … Read more
The second version is calling string’s default ctor and then string’s copy-assignment operator — there could definitely be (minor) efficiency losses compared to the first one, which directly calls c’s copy-ctor (e.g., depending on string’s implementation, there might be useless allocation-then-release of some tiny structure). Why not just always use the right way?-)
Initialization list is part of constructor’s definition so you need to define it at the same place you define constructor’s body. This means that you can have it either in your header file: public: Square(int row, int col): m_row(row), m_col(col) {}; or in .cpp file: Square::Square(int row, int col) : m_row(row), m_col(col) { // … … Read more
In C++, initializer lists are necessary because of a few language features that are either not present in Java or work differently in Java: const: In C++, you can define a fields that are marked const that cannot be assigned to and must be initialized in the initializer list. Java does have final fields, but … Read more