c ++中的不完整类型

Question

I have declared DynArray var_name in c++, but while compiling it gives me an error "incomplete type not allowed" I tried to search but nothing came up with an example of dynamic array. Could anyone please explain the error? Thanks.

Answer 1

If you are defining a member variable x to your class C in a header file Ch , you must include the header of the class X ( Xh ) in Ch . If however, you are just storing a pointer to X as a member of C , then you can forward declare class X; before you declare class C{...}; and then in the definition file C.cpp , you must include Xh if you access any members of x .

Answer 2

"incomplete type not allowed" usually means that a class has been declared but not defined at a point at which its complete definition is needed.

This sometimes happens because of a circular dependency in the headers,

class A's definition depends on class B's definition and visa-versa - causing Ah to include Bh, and then Bh try's to include Ah but can't because the header guard is already defined, so it skips, but then only gets a fwd decl of A.