Question

As the title says. How would I create an instance of a class that is globally available(for example I have a functor for printing and i want to have a single global instance of this(though the possibility of creating more)).

Answer 1

Going to all the effort of making a singleton object using the usual pattern isn’t addressing the second part of your question – the ability to make more if needed. The singleton ‘pattern’ is very restrictive and isn’t anything more than a global variable by another name.

// myclass.h  class MyClass { public:     MyClass();     void foo();     // ... };  extern MyClass g_MyClassInstance;  // myclass.cpp  MyClass g_MyClassInstance;  MyClass::MyClass() {     // ... } 

Now, in any other module just include myclass.h and use g_MyClassInstance as usual. If you need to make more, there is a constructor ready for you to call.