CODEWITHSUNDEEP
cpointersstruct
Ali Zahr
Ali Zahr

Reputation: 64

Defining a pointer in a struct

I've create a structure Person and had these variables in it, then I added a new field named father and its type is pointer to a person. I have to initialize the data of FJames as following: fname = Whatever, lname = Bond, age = 80, job = Farmer, father = NULL

Then initialize the data of James as following: fname = James, lname = Bond, age = 40, job = Actor, father = FJames

Then display all the data. I'm getting an error " initializing struct Person * with an expression of incompatible type "Person" What to do? :/ I don't even think I'm doing it right, please help!

/#include <stdio.h>

typedef struct {
    int age;
    char *fname;
    char *lname;
    char *job;
    struct Person *father;
}Person;

int main(int argc, const char * argv[])
{

    Person James;
    Person FJames = {80,"Whatever","Bond","Painting",NULL};
    James.age = 40;
    James.fname = "James";
    James.lname = "Bond";
    James.job = "Engineering";
    James.father = FJames;

}

Upvotes: 1

Views: 98

Answers (5)

Jakub Januszkiewicz
Jakub Januszkiewicz

Reputation: 4418

That last line should be

James.father = &FJames;

The father field is a pointer, but FJames is a Person. You can use & to get the address of FJames.

Edit

The struct definition should also be changed in addition to that, in one of the ways aragaer suggested, e.g.:

typedef struct s_Person {
    // ...
    struct s_Person *father;
} Person;

Upvotes: 0

Alex Reynolds
Alex Reynolds

Reputation: 96984

Here's a working program:

#include <stdio.h>
#include <stdlib.h>

typedef struct Person {
    int age;
    char *fname;
    char *lname;
    char *job;
    struct Person *father;
} Person;

int main(int argc, const char * argv[])
{

    Person James;
    Person FJames = {80,"Whatever","Bond","Painting",NULL};
    James.age = 40;
    James.fname = "James";
    James.lname = "Bond";
    James.job = "Engineering";
    James.father = &FJames;

    fprintf(stdout, "%d\t%s\t%s\t%s\tpops:\t%s\t%s\n", James.age, James.fname, James.lname, James.job, (James.father)->fname, (James.father)->lname);

    return EXIT_SUCCESS;
}

Corrections:

  1. You should correct your typedef so that it declares Person.
  2. When setting James.father it should dereference FJames so that you are setting it to the value of the pointer to FJames.
  3. Your main() function should return an int, so return EXIT_SUCCESS (defined in stdlib.h) to note that you exited properly.

Advice:

  1. When dereferencing properties of James.father, use precedence and arrow notation to dereference its values.
  2. If you are using gcc, compile with -Wall option to enable all compilation warnings. This will help note warnings that point where corrections are needed.

Upvotes: 0

bazza
bazza

Reputation: 8444

James.father = &FJames should be what you need.

There are other minor problems. These days initialising a char* from a string constant is frowned upon, because char* implies that the memory being pointed at can be altered.

Upvotes: 0

aragaer
aragaer

Reputation: 17858

You don't declare struct Person actually.

You're declaring anonymous structure and typedef it to person. You then should use it as just Person, not struct Person.

struct Person {
    struct Person *father; // this will work
}

or if you want typedef

typedef struct s_Person {
    struct s_Person *father
} Person;

Upvotes: 1

sandymatt
sandymatt

Reputation: 5612

typedef struct {
    int age;
    char *fname;
    char *lname;
    char *job;
    struct Person *father; // << This is a pointer to a Person
} Person;


James.father = FJames;

FJames is not a Person*. He's a Person. You need to malloc him in order to get a Person*. Or take his address with &

This code has some other issues, but that's the one that's giving you the error in question.

Upvotes: 0

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