error request for member in which is of non-class type

Question

I have a class with two constructors  one that takes no arguments and one that takes one argument   Creating objects using the constructor that takes one argument works as expected  However  if I create objects using the constructor that takes no arguments  I get an error   For instance  if I compile this code  using g   4 0 1      class Foo     public      Foo           Foo int a          void bar           int main          this works      Foo foo1 1     foo1 bar          this does not      Foo foo2      foo2 bar       return 0          I get the following error   nonclass cpp  In function    int main int  const char        nonclass cpp 17  error  request for member    bar    in    foo2     which is of non-class type    Foo           Why is this  and how do I make it work

User · Answer

I ran into a case where I got that error message and had

Foo foo(Bar());

and was basically trying to pass in a temporary Bar object to the Foo constructor. Turns out the compiler was translating this to

Foo foo(Bar(*)());

that is, a function declaration whose name is foo that returns a Foo that takes in an argument -- a function pointer returning a Bar with 0 arguments. When passing in temporaries like this, better to use Bar{} instead of Bar() to eliminate ambiguity.

User · Answer

Certainly a corner case for this error  but I received it in a different situation  when attempting to overload the assignment operator    It was a bit cryptic IMO  from g   8 1 1     include  lt cstdint gt   enum DataType     DT INT32    DT FLOAT     struct PrimitiveData     union MyData         int32 t i      float f      data     enum DataType dt     template lt typename T gt    void operator  T data          switch dt              case DT INT32                  data i   data          break                case DT FLOAT                  data f   data          break                default                  break                        int main       struct PrimitiveData pd    pd dt   DT FLOAT    pd   3 4f     return 0      I received 2  identical  errors  error  request for member    i     and  f   in    data     which is of non-class type    float       The equivalent error for clang is  error  member reference base type  float  is not a structure or union   for the lines data i   data  and data f   data    Turns out the compiler was confusing local variable name  data  and my member variable data   When I changed this to void operator  T newData  and data i   newData   data f   newData   the error went away

User · Answer

MykolaGolubyev has already given wonderful explanation  I was looking for a solution to do somthing like this MyClass obj   MyAnotherClass     but the compiler was interpreting it as a function declaration   C  11 has braced-init-list  Using this we can do something like this   Temp t String       However  this   Temp t String       throws compilation error as it considers t as of type Temp String           include  lt iostream gt   class String   public      String const char  str   ptr str                std  cout  lt  lt   Constructor     lt  lt  str  lt  lt  std  endl            String void   ptr nullptr                std  cout  lt  lt   Constructor   lt  lt  std  endl            virtual  String void                std  cout  lt  lt   Destructor   lt  lt  std  endl         private      const char  ptr      class Temp   public      Temp String in   str in                std  cout  lt  lt   Temp Constructor   lt  lt  std  endl             Temp    str String  hello                  std  cout  lt  lt   Temp Constructor  2   lt  lt  std  endl            virtual  Temp void                std  cout  lt  lt   Temp Destructor   lt  lt  std  endl             virtual String get str                 return str         private      String str      int main void        Temp t String        Compiles Success         Temp t String        Doesn t compile  Considers  t  as of type  Temp String            t get str       dummy statement just to check if we are able to access the member     return 0

User · Answer

Adding to the knowledge base  I got the same error for   if class iter- gt num     int iter    Even though the IDE gave me the correct members for class iter  Obviously  the problem is that  anything   iterator doesn t have a member called num so I need to dereference it  Which doesn t work like this   if  class iter- gt num     int iter       apparently  I eventually solved it with this   if   class iter - gt num     int iter    I hope this helps someone who runs across this question the way I did

User · Answer

I was having a similar error  it seems that the compiler misunderstand the call to the constructor without arguments  I made it work by removing the parenthesis from the variable declaration  in your code something like this   class Foo     public      Foo           Foo int a          void bar           int main          this works      Foo foo1 1     foo1 bar          this does not      Foo foo2     Without         foo2 bar       return 0

User · Answer

Foo foo2      change to  Foo foo2    You get the error because compiler thinks of  Foo foo2     as of function declaration with name  foo2  and the return type  Foo    But in that case If we change to Foo foo2   the compiler might show the error     call of overloaded    Foo      is ambiguous

User · Answer

Just for the record    It is actually not a solution to your code  but I had the same error message when incorrectly accessing the method of a class instance pointed to by myPointerToClass  e g   MyClass  myPointerToClass   new MyClass    myPointerToClass aMethodOfThatClass      where  myPointerToClass- gt aMethodOfThatClass      would obviously be correct

User · Answer

If you want to declare a new substance with no parameter  knowing that the object have default parameters  don t write    type substance1      but   type substance

User · Answer

Parenthesis is not required to instantiate a class object when you don t intend to use a parameterised constructor   Just use  Foo foo2   It will work

[c++] error: request for member '..' in '..' which is of non-class type

Examples related to c++