This example shows you how to return a structure from a function.
Think of the following when reading this:
- The struct is created locally and return.
- By creating the struct in a dedicated function, we can easily implement error checking that will always be present.
- This also works nicely if you need to read multiple structs into a struct array.
- This also works for when reading from files.
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/** * File: car_return.c * Author: Risto Heinsar * Created: 02.02.2015 * Modified 13.02.2024 * * Description: Example how to return a copy of a struct from a function */ #include <stdio.h> #include <stdlib.h> #define REG_LEN 10 #define FIELD_LEN 128 typedef struct car { char regNum[REG_LEN]; char regCity[FIELD_LEN]; char manufacturer[FIELD_LEN]; char model[FIELD_LEN]; int year; } car; car EnterCarData(void); void PrintCarData(car autoMobile); void GetString(char str[], int len); int GetPositiveInt(void); int main(void) { /* Store the returned struct */ car machine = EnterCarData(); PrintCarData(machine); return EXIT_SUCCESS; } /** * Description: Reads the details of a car into a structure and returns it. * * Parameters: none * * Return: car structure, details of an automobile. */ car EnterCarData(void) { /* Declare a temporary struct */ car vehicle; /* Populate the members of the struct */ printf("Enter the registration number of the car\n"); GetString(vehicle.regNum, REG_LEN); printf("Enter the registration city of the car\n"); GetString(vehicle.regCity, FIELD_LEN); printf("Enter the manufacturer of the car\n"); GetString(vehicle.manufacturer, FIELD_LEN); printf("Enter the model number of the car\n"); GetString(vehicle.model, FIELD_LEN); printf("Enter the year of manufacturing\n"); vehicle.year = GetPositiveInt(); return vehicle; } /** * Description: Outputs the details of an automobile * * Parameters: automobile, car structure with the details of a car * * Return: none */ void PrintCarData(car autoMobile) { printf("%s %s %s %s %d\n", autoMobile.regNum, autoMobile.regCity, autoMobile.manufacturer, autoMobile.model, autoMobile.year); } /** * Description: Reads a positive int from the keyboard, reprompts if * input is not positive * * Parameters: none * * Return: Positive integer from stdin */ int GetPositiveInt(void) { char temp[FIELD_LEN]; while (1) { /* Get value as a string and convert to int */ GetString(temp, FIELD_LEN); int ans = atoi(temp); /* Return if result matches criteria*/ if (ans > 0) return ans; /* Reprompt on invalid input */ printf("Error! Input must be a positive number!\n"); } } /** * Description: Reads a string from stdin and fixes the newline character * * Parameters: str - read string to be stored here * len - maximum length for str * * Return: none */ void GetString(char *str, int len) { /* Grab user input */ fgets(str, len, stdin); /* Identify the newline (if present) */ char *pStr = str; while (*pStr != '\n' && *pStr != '\0') pStr++; /* Get rid of the trailing newline */ *pStr = '\0'; } |