Failed to compile in C++

[philuu12]

Hi,

I got the following snippet of codes which gave me the following
compile errors. I would really appreciate if anyone could tell
me what I have done wrong.

     1  #include <iostream>
     2  #include <string>
     3
     4  class State;
     5  class StateMachineInterface
     6  {
     7     public:
     8          virtual void gotApplication() { }
     9          virtual void checkApplication() { }
    10          virtual void setState(State* s) { }
    11  };
    12
    13  // class WaitingState;
    14  class ConcreteStateMachine : public StateMachineInterface
    15  {
    16     public:
    17          ConcreteStateMachine(int n)
    18          {
    19             waitingState    = new WaitingState(this);
    20             state           = waitingState;
    21          }
    22
    23          void gotApplication()
    24          {   cout << state->gotApplication(); }
    25
    26          void checkApplication()
    27          {  cout << state->checkApplication();  }
    28
    29          virtual void setState(State* s)
    30          {  state = s;  }
    31
    32     private:
    33          State* waitingState;
    34          State* state;
    35  };
    36
    37  class State
    38  {
    39     public:
    40          virtual string gotApplication() = 0;
    41          virtual string checkApplication() =  0;
    42  };
    43
    44  class WaitingState : public State
    45  {
    46     public:
    47          WaitingState(StateMachineInterface* a)
    48          {  automat = a; }
    49
    50          string gotApplication()
    51          {
    52            automat->setState(automat->getGotApplicationState());
    53             return "Thanks for the application.";
    54          }
    55
    56          string checkApplication()
    57          {   return "You have to submit an application.";  }
    58
    59     private:
    60          StateMachineInterface* automat;
    61  };
    62
    63  int main()
    64  {    }
 
 

Compile errors
==========================
/class/PATTERN-DESIGN/state% g++ example.cc
example.cc: In method `ConcreteStateMachine::ConcreteStateMachine(int)':
example.cc:19: parse error before `('
example.cc: In method `void ConcreteStateMachine::gotApplication()':
example.cc:24: no matching function for call to `State::gotApplication ()'
example.cc: In method `void ConcreteStateMachine::checkApplication()':
example.cc:27: no matching function for call to `State::checkApplication ()'
example.cc: In method `class basic_string<char,string_char_traits<char>,__defau lt_alloc_template<false,0> > WaitingState::gotApplication()':
example.cc:52: no matching function for call to `StateMachineInterface::getGotApplicationState ()'
======================================

To start off, why does it complain about lines 19 and 24?

Thanks in advance,

PL

[johny10151981]

Where did you define waitingState????

[philuu12]

Johny10151981:
I defined waitingState as an object pointer in line 34. Are u suggesting
that waitingState as an pointer is causing the problem here?
thanks,

PL

[weaknessforcats]

You are using waitingState as a type before the compiler has seen the class definition. Therefore, waitingState is not a valid type.

Use a forward reference to waitingState before the ConcreteStateMachine class declaration:

class waitingState; //forward reference
 
class ConcreteStateMachine ...etc

This is enough info for the compier to accept a waitingState*

[philuu12]

Thanks weaknessforcats, it worked after I forward-declared the waitingState class, and moved the codes around. PL