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I have a C++ class with two member variables
std::map<int, Node*> a;
and
std::set<Node*> b;
A style checker used at my University requires all member variables to be initialized in the constructor of the class. How can these member variables a and b be initialized to empty in the constructor of the class they are in?
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In C++11, the language has been extended to allow specifying an initializer in the declaration, but this is just a shorthand—the actual initialization still takes place at the top of the constructor. Initialization of data members will also still occur in order of declaration.
To initialize a class member variable, put the initialization code in a static initialization block, as the following section shows. To initialize an instance member variable, put the initialization code in a constructor.
zero-initialization – Applied to static and thread-local variables before any other initialization. If T is scalar (arithmetic, pointer, enum), it is initialized from 0 ; if it's a class type, all base classes and data members are zero-initialized; if it's an array, each element is zero-initialized.
As both std::set and std::map have "user"-declared default constructors they will be initialized implicitly however you construct your class. You don't have to do anything special to conform with the "style" guide.
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