How do you forward a declared class in C++?

In C++, Forward declarations are usually used for Classes. In this, the class is pre-defined before its use so that it can be called and used by other classes that are defined before this. Example: // Forward Declaration class A class A; // Definition of class A class A{ // Body };

How do you declare a class in namespace?

Forward Declaration of Classes Within Namespaces

1. Define the namespace with the “using namespace” keyword and then declare the class: using namespace A::B; class CClassName;
2. Define the forward declaration like this: namespace A { namespace B { class CClassName; } }

Can you forward declare a struct C++?

In C++, classes and structs can be forward-declared like this: class MyClass; struct MyStruct; In C++, classes can be forward-declared if you only need to use the pointer-to-that-class type (since all object pointers are the same size, and this is what the compiler cares about).

How to forward declare class which is in a namespace?

To forward declare class type a in a namespace ns1: namespace ns1 { namespace ns2 { //…. namespace nsN { class a; } //…. } } Your are using a a member of consumer which means it needs concrete type, your forward declaration won’t work for this case. Thanks for contributing an answer to Stack Overflow!

How to forward declare a class in a header file?

I am trying to use forward declarations in header files to reduce #includes used and hence reduce dependencies where users include my header file. However, I am unable to forward decalre where namespaces are used.

What do you mean by forward declaration in C + +?

What are Forward declarations in C++. Forward Declaration refers to the beforehand declaration of the syntax or signature of an identifier, variable, function, class, etc. prior to its usage (done later in the program). In C++, Forward declarations are usually used for Classes. In this, the class is pre-defined before its use so that it can be

How does class declaration work in cppreference.com?

Declares a class type which will be defined later in this scope. Until the definition appears, this class name has incomplete type. This allows classes that refer to each other: and if a particular source file only uses pointers and references to the class, this makes it possible to reduce #include dependencies: