#Circular reference of classes

24 messages · Page 1 of 1 (latest)

pale harbor
#

So here's a toy example of what I want:

#include <iostream>
#include <vector>

class Boss;

class Worker{
  Boss& boss; // using a reference here
  int salary;
public:
  Worker(Boss& b, int s){
    this->boss = b;
    this->salary = s;
  }
  // other logic, whatever
};

class Boss{
  std::vector<Worker> workers;
public:
  // constructors, etc
  Boss(){}
  Worker hireSomebody(){
    Worker w = Worker(*this, 25);
    // I've hard coded "25" here, but assume that I do some calculations and whatnot to obtain that value.
    return w;
  }

};



int main() {
    // Write C++ code here
    std::cout << "Hello world!";

    return 0;
}

I know that I can probably do it some other way (by creating a getHired() function from a worker, or something similar), but How do I do it this way?
My only requirement is that the "owner" object is "constructing" a "child" object.

ofcourse, when I try to compile this, I get something similar to invalid use of incomplete type ‘class Worker’ and return type ‘class Worker’ is incomplete

elder oakBOT
#

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mellow pike
#

move Boss below Worker

#

And then forward declare Boss before Worker

nimble heart
#

You'll need to forward declare classes and also possibly define members separately from the class body

mellow pike
#

so:

class Boss;

class Worker {
  // body
};

class Boss {
  // body
};
pale harbor
#

i see

#

ok so here is my example code again

#include <iostream>
#include <vector>

class Boss;

class Worker{
  Boss& boss; // using a reference here
  int salary;
public:
  Worker(Boss& b, int s){
    this->boss = b;
    this->salary = s;
  }
  // other logic, whatever
};

class Boss{
  std::vector<Worker> workers;
public:
  // constructors, etc
  Boss(){}
  Worker hireSomebody(){
    Worker w = Worker(*this, 25);
    // I've hard coded "25" here, but assume that I do some calculations and whatnot to obtain that value.
    return w;
  }

};



int main() {
    // Write C++ code here
    std::cout << "Hello world!";

    return 0;
}
#

I still get the same error

# 
/tmp/xKnfUrMlJn.cpp: In constructor 'Worker::Worker(Boss&, int)':
/tmp/xKnfUrMlJn.cpp:11:3: error: uninitialized reference member in 'class Boss&' [-fpermissive]
   11 |   Worker(Boss& b, int s){
      |   ^~~~~~
/tmp/xKnfUrMlJn.cpp:8:9: note: 'Boss& Worker::boss' should be initialized
    8 |   Boss& boss; // using a reference here
      |         ^~~~
/tmp/xKnfUrMlJn.cpp:12:11: error: invalid use of incomplete type 'class Boss'
   12 |     this->boss = b;
      |     ~~~~~~^~~~
/tmp/xKnfUrMlJn.cpp:5:7: note: forward declaration of 'class Boss'
    5 | class Boss;
      |       ^~~~
nimble heart
#

You can't use Boss before it's defined

#

You can have a reference or pointer to Boss, but you can't do anything with it

#

this->boss = b; is invoking the copy constructor and is also improper initialization of a reference

pale harbor
#

oh

nimble heart
#

Write you constructor as Worker(Boss& b, int s) : b(b), s(s) {}

pale harbor
#

i thought they worked like pointers

pale harbor
nimble heart
#

They have a lot in common with pointers, just some syntactic differences

pale harbor
#

ok imma try this out too

#

oh hey it actually worked

#

thanks man

elder oakBOT
#

Thank you and let us know if you have any more questions!

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pale harbor
nimble heart
#

Excellent