static-members

I need to create a static object inside a class definition. It is possible in Java, but in C++ I get an error: ../PlaceID.h:9:43: error: invalid use of incomplete type ‘class PlaceID’ ../PlaceID.h:3:7: error: forward declaration of ‘class PlaceID’ ../PlaceID.h:9:43: error: invalid in-class initialization of static data My class looks like this: #include <string> class PlaceID { public: inline PlaceID(const std::string placeName):mPlaceName(placeName) {} const static PlaceID OUTSIDE = PlaceID(""); private: std::string mPlaceName; }; Is it possible to make an object of a class inside this class?

In the following, static constexpr member L is initialized in-class A and then passed by value or by (universal) reference. The latter fails in Clang but not in GCC, and behaviour is slightly different for member/non-member functions. In more detail: #include <iostream> using namespace std; struct A { static constexpr size_t L = 4; template <typename T> void member_ref(T&& x) { cout << std::forward<T>(x) << endl; } template <typename T> void member_val(T x) { cout << x << endl; } }; template <typename T> void ref(T&& x) { cout << std::forward<T>(x) << endl; } template <typename T> void val(T x

Accessing static class member functions or variables, can be done in two ways: through an object ( obj.member_fun() or obj.member_var ) or through the class ( Class::member_fun() or Class::member_var ). However, in constexpr functions, Clang gives an error on the object access and requires to use class access: struct S { constexpr static auto s_v = 42; constexpr static auto v() { return s_v; } }; #define TEST 1 constexpr auto foo(S const& s [[maybe_unused]]) { #if TEST constexpr auto v = s.v(); // ERROR for clang, OK for gcc #else constexpr auto v = S::v(); // OK for clang and gcc #endif

I'm working on my Window Application and i'm using some static members. public class MyParameter { public static string connectionString = "..."; } Now if I install my application on computer and open two instance of same application. Will 'connectionString' common to the two instances?? Or every instance has its connectionString ? Tigran The variable static or not is a part of your application memory. When you open 2 instances of your application you create two distinct memory locations in the OS, so there is not any relation between those 2 variables at all. If you want to create one

I'm writing some code where I need to have a class variable that's a static int array. I understand that I can do this with something like this in the header file, A.h: #ifndef A_H_ #define A_H_ class A { public: static const int a[]; }; const int A::a[] = {1,2}; #endif This works just fine if I'm then including this header in only one other file, something like the following, main.cpp: #include "A.h" #include <iostream> using namespace std; int main() { A myA; cout << "0: " << myA.a[0] << endl; cout << "1: " << myA.a[1] << endl; } But suppose I need my class A to be a bit more complicated,

I have gone through msdn where it is written that all the static classes are thread safe. Well that article is meant for version 1.1... http://msdn.microsoft.com/en-us/library/d11h6832(v=vs.71).aspx All public static members (methods, properties, fields, and events) within the .NET Framework support concurrent access within a multithreaded environment. Therefore, any .NET Framework static member can be simultaneously invoked from two threads without encountering race conditions, deadlocks, or crashes. No, it doesn't say that static classes are thread safe, it says that public static members