This was discussed on usenet some time ago, while i was trying to answer another question on stackoverflow: Point of Instantiation of Static Data Members. I think it’s worth reducing the test-case, and considering each scenario in isolation, so let’s look at it more general first: struct C { C(int n) { printf(“%d\n”, n); } … Read more
Excuse me when I answer your questions out-of-order, it makes it easier to understand this way. When static variable is declared in a header file is its scope limited to .h file or across all units. There is no such thing as a “header file scope”. The header file gets included into source files. The … Read more
Anywhere in one compilation unit (usually a .cpp file) would do: foo.h class foo { static const string s; // Can never be initialized here. static const char* cs; // Same with C strings. static const int i = 3; // Integral types can be initialized here (*)… static const int j; // … OR … Read more
Just define it in the header: template <typename T> struct S { static double something_relevant; }; template <typename T> double S<T>::something_relevant = 1.5; Since it is part of a template, as with all templates the compiler will make sure it’s only defined once.
The class declaration should be in the header file, or in the source file, if the class is not used in other files. // foo.h class foo { private: static int i; }; However, the initialization should be in the source file. // foo.cpp int foo::i = 0; If the initialization is in the header … Read more
You have to define your static member outside the class definition and provide the initializer there. First // In a header file (if it is in a header file in your case) class A { private: static const string RECTANGLE; }; and then // In one of the implementation files const string A::RECTANGLE = “rectangle”; … Read more
Enums are great for lightweight state information. For example, your color enum (excluding blue) would be good for querying the state of a traffic light. The true color along with the whole concept of color and all its baggage (alpha, color space, etc) don’t matter, just which state is the light in. Also, changing your … Read more
The first question is why you need to serialize the static members? Static members are associated with the class, not the instances, so it does not make sense to include them when serializing an instance. The first solution is to make those members not static. Or, if those members are the same in the original … Read more
The Standard requires (section 9.4.2): A static data member of literal type can be declared in the class definition with the constexpr specifier; if so, its declaration shall specify a brace-or-equal-initializer in which every initializer-clause that is an assignment-expression is a constant expression. In your “second attempt” and the code in Ilya’s answer, the declaration … Read more
but in typescript this.constructor.prop causes error “TS2339: Property ‘prop’ does not exist on type ‘Function’”. Typescript does not infer the type of constructor to be anything beyond Function (after all … the constructor might be a sub class). So use an assertion: class SomeClass { static prop = 123; method() { (this.constructor as typeof SomeClass).prop; … Read more