Home/ Questions/Steps to fix the error “ does not name a type in c++”
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Jules Lagarde
  • 10
Asked: 2022-05-17T12:37:14+00:00 In:

Steps to fix the error “ does not name a type in c++”

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I am trying to write a cpp that returns an invalid answer. I don’t know where the incorrect command is in the “does not name a type in c++.” My detail is:

class User
 {
 public:
  MyMessageBox dataMsgBox;
 };
 
 class MyMessageBox
 {
 public:
  void sendMessage(Message *msg, User *recvr);
  Message receiveMessage();
  vector<Message> *dataMessageList;
 };

and I end up with the warning message:

MyMessageBox does not name a type

Pls, suggest the best answer to fix it.

does not name a type
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2 Answers

  1. Best Answer
    Expert

    The cause: I think the cause is that C++ compilers only process input once. Each class you use has to be defined first. But you use MyMessageBox before you define it. 

    The solution: Before you use the prototype, you must declare it. It means that you need to swap the types as the following:

    class User;

class MyMessageBox
{
public:
 void sendMessage(Message *msg, User *recvr);
 Message receiveMessage();
 vector<Message> *dataMessageList;
};

class User
{
public:
 MyMessageBox dataMsgBox;
};
    • 20
    1. Forward declare User
    2. Before User, put the declaration of MyMessageBox
    • 8

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