C++ pointer trouble

[Octon22]

When you have several different classes that interact, how do you
avoid compile errors when doing the following:

class Person
{
City* places; // array of pointers to cities he's been to
};

class City
{
vector <Person> population; // array of houses that are within this
city
};


the compiler gets to the definition of class Person and doesn't
recognize 'City' as a class. Functions don't have this problem
because you can declare prototypes before defining the function body.
How can I solve this problem when it comes to classes? Thanks.

 

[Sharad Kala]

When you have several different classes that interact, how do you
avoid compile errors when doing the following:

class Person
{
City* places; // array of pointers to cities he's been to
};

class City
{
vector <Person> population; // array of houses that are within this
city
};


the compiler gets to the definition of class Person and doesn't
recognize 'City' as a class. Functions don't have this problem
because you can declare prototypes before defining the function body.
How can I solve this problem when it comes to classes? Thanks.

What you require is called a forward declaration .

class City; // Forward declaration
class Person
{
City* places; // array of pointers to cities he's been to
};

Best wishes,
Sharad

 

[David Harmon]

When you have several different classes that interact, how do you
avoid compile errors when doing the following:

This issue is covered in the topic "[34.9] How can I create two classes
that both know about each other?" of Marshall Cline's C++ FAQ. It is
always good to check the FAQ before posting. You can get the FAQ at:
http://www.parashift.com/c++-faq-lite/

 

[Dan Cernat]

When you have several different classes that interact, how do you
avoid compile errors when doing the following:

class Person
{
City* places; // array of pointers to cities he's been to

^^^^^^^^^^^^^^^^^^^^ array of cities
City** places; // array of pointers to cities;

 

[Frank Puck]

When you have several different classes that interact, how do you
avoid compile errors when doing the following:

class Person
{
City* places; // array of pointers to cities he's been to
};

class City
{
vector <Person> population; // array of houses that are within this
city
};


the compiler gets to the definition of class Person and doesn't
recognize 'City' as a class. Functions don't have this problem
because you can declare prototypes before defining the function body.
How can I solve this problem when it comes to classes? Thanks.

#include <set>

class City; // forward declaration so the compiler knows what City stands
for.
class Person
{
// set is ideal for your task
std::set<City*> places;
}


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