Function to Create a Contact

Part of the Logic & Flow section of Coddy's C journey — lesson 51 of 63.

Challenge

Easy

Building on your Contact struct from the previous lesson, create a function that dynamically allocates memory for a new contact. Your program should:

Use the same Contact struct definition from the previous lesson with members:
- A character array name with size 50
- A character array phone with size 20
- A character array email with size 40
- An integer age
Write a function named createContact that:
- Takes no parameters
- Returns a pointer to a Contact struct
- Uses malloc() to dynamically allocate memory for one Contact struct
- Checks if the memory allocation was successful:
  - If allocation fails (returns NULL), prints Memory allocation failed and returns NULL
  - If allocation succeeds, prints Contact created successfully
- Initializes all struct members to default values using the arrow operator:
  - Sets name to an empty string using contactPtr->name[0] = '\0';
  - Sets phone to an empty string using contactPtr->phone[0] = '\0';
  - Sets email to an empty string using contactPtr->email[0] = '\0';
  - Sets age to 0 using contactPtr->age = 0;
- Returns the pointer to the newly created contact
In the main function:
- Declare a pointer to a Contact struct named newContact
- Call the createContact function and assign the returned pointer to newContact
- Check if the contact creation was successful:
  - If newContact is NULL, print Failed to create contact and exit the program
  - If successful, print Contact initialized with default values
- Display the initialized contact information using the arrow operator in this exact format:
  - Default Contact Values:
  - Name: [name] (will be empty)
  - Phone: [phone] (will be empty)
  - Email: [email] (will be empty)
  - Age: [age] (will be 0)
- Free the dynamically allocated memory using free(newContact)
- Print Memory freed successfully

This challenge introduces the concept of factory functions - functions that create and return pointers to dynamically allocated structs. You'll practice dynamic memory allocation, proper error checking, struct initialization through pointers, and memory cleanup.

Try it yourself

#include <stdio.h>
#include <string.h>

// TODO: Define the Contact struct here
struct Contact {
    char name[50];
    char phone[20];
    char email[40];
    int age;
};

int main() {
    // TODO: Create a Contact variable named person
    struct Contact person;
    
    // Read input values
    scanf("%s", person.name);
    scanf("%s", person.phone);
    scanf("%s", person.email);
    scanf("%d", &person.age);
    
    // TODO: Write your validation and output code below
    if (person.age < 0 || person.age > 120) {
        printf("Invalid age");
        return 0;
    }
    
    if (strlen(person.phone) < 10) {
        printf("Invalid phone number");
        return 0;
    }
    
    printf("Contact Information:\n");
    printf("Name: %s\n", person.name);
    printf("Phone: %s\n", person.phone);
    printf("Email: %s\n", person.email);
    printf("Age: %d\n", person.age);
    
    printf("Name length: %lu\n", strlen(person.name));
    
    if (person.age >= 0 && person.age <= 17) {
        printf("Category: Minor");
    } else if (person.age >= 18 && person.age <= 64) {
        printf("Category: Adult");
    } else {
        printf("Category: Senior");
    }
    
    return 0;
}

All lessons in Logic & Flow

3Character Arrays and Strings

Strings as char Arrays The Null Terminator String Input with scanf Using strlen()Using strcpy()Using strcat()Using strcmp()Recap: Basic String Functions

6Memory Management

Stack vs. Heap Memory Dynamic Allocation - malloc()Using sizeof() for Allocation Checking Allocation Failure Freeing Memory with free()Allocating with calloc()Recap: Dynamic Array

9Project: Simple Contact Entry

Project: Define Contact StructFunction to Create a Contact Project lesson

Function to Populate a Contact

Function to Display a Contact

Putting It All Together