PHP doesn’t support any friend-like declarations. It’s possible to simulate this using the PHP5 __get and __set methods and inspecting a backtrace for only the allowed friend classes, although the code to do it is kind of clumsy. There’s some sample code and discussion on the topic on PHP’s site: class HasFriends { private $__friends … Read more
It sounds like you want to change: friend ostream& operator << (ostream& out, const Base<T>& e); To: template<class T> friend ostream& operator << (ostream& out, const Base<T>& e);
Try putting the B definition before A’s: class A; // forward declaration of A needed by B class B { public: // if these require full definition of A, then put body in implementation file void fB(A& a); // Note: no body, unlike original. void fB2(A& a); // no body. }; class A { public: … Read more
I like, in decreasing preference: passkey friend idiom passkey-door friend idiom pass-door friend idiom key-door friend idiom partial-friend idiom restricted-friend idiom I moved away from the key-lock/key-keyhole naming scheme to the pass naming scheme, which grew on me.
Quote from C++ FAQ which I think describes the situation with friend and encapsulation very well. No! If they’re used properly, they enhance encapsulation. You often need to split a class in half when the two halves will have different numbers of instances or different lifetimes. In these cases, the two halves usually need direct … Read more
I was surprised about this (and as a result deleted a previous incorrect answer). The C++03 standard says in 11.4: An elaborated-type-specifier shall be used in a friend declaration for a class. Then to make sure there’s no misunderstanding, it footnotes that with: The class-key of the elaborated-type-specifier is required. GCC is the only compiler … Read more
There is a way to read unexported members using reflect (in Go < 1.7) func read_foo(f *Foo) { v := reflect.ValueOf(*f) y := v.FieldByName(“y”) fmt.Println(y.Interface()) } However, trying to use y.Set, or otherwise set the field with reflect will result in the code panicking that you’re trying to set an unexported field outside the package. … Read more
C++ Standard ISO/IEC 14882:2003(E) 7.3.1.2 Namespace member definitions Paragraph 3 Every name first declared in a namespace is a member of that namespace. If a friend declaration in a non-local class first declares a class or function (this implies that the name of the class or function is unqualified) the friend class or function is … Read more
I’d go with “C++ Coding Standards: 101 Rules, Guidelines, and Best Practices”: if you can do it as non-member function, do it as non-member function (in the same namespace). One of the reasons: it works better with implicit type conversion. An Example: You have a complex class with an overloaded operator*. If you want to … Read more
friend inline bool operator==(MonitorObjectString& lhs, MonitorObjectString& rhs) { return(lhs.fVal==rhs.fVal); } is sometimes called friend definition, because it is a friend declaration that also defines the function. It will define the function as a non-member function of the namespace surrounding the class it appears in. Actually, the inline there is redundant: It’s implicitly declared inline if … Read more