Codes

Returning multiple values from a method?

Often we come across this question, how to return multiple values from a method? The snippets below describes the various approaches possible.

Normal circumstances

int f1()

{
    int x =10;
    return x;
}

The above scenario describes the most basic way a value can be returned from a method. We will expand this base to return multiple value from a method.

Using structures

This is the most efficient way to return multiple values from a method. A structure can be declared to hold as many values as desired. And the method return type can return the structure type. Below snippets shows how to do this using both pointer way and non-pointer way.

Without pointers

#include

#include   // required for strcpy() method

// declare a structure to hold multiple values

struct record

{

   int roll;

   float marks;

   char str[50];

};

// define an initialization method which return a struct

struct record init()

{

   struct record rec;

   rec.roll = 1;

   rec.marks = 10;

   strcpy(rec.str,"default");

   return rec;

}

int main()

{

   struct record temp;

   temp = init();

   printf("Default record\n Roll = %d\n Marks = %f\n Name = %s", temp.roll, temp.marks, temp.str);

   return 0;

}

Output:

Default record

Roll = 1;

Marks = 10.000000

Name = default

With pointers

#include

#include   // required for strcpy() method

#include   // required for malloc() method

// declare a struct

struct record

{

   int roll;

   float marks;

   char* str;

};

// define an initialization method to return a struct

struct record* init()

{

   // declare a pointer of type struct record

   struct record *rec;  

   // allocate some blocks of memory to the pointer 

   // type-casting infront of malloc is required because malloc allocates a memory area and return a void type

   rec = (struct record*) malloc( sizeof( struct record )); 

   // assign values to the struct members

   // since rec is a pointer type variable, ->(arrow) should be used instead of a .(dot) to access memberes

   rec->roll = 1;

   rec->marks = 10; 

   // since str is a pointer, we need to allocate memory to this too to have it hold some values

   rec->str = (char*) malloc(100);

   strcpy(rec->str,"default");

   // return the pointer. We don't need to return *rec, since rec is already declared as *rec

    return rec;

}

int main()

{

   // declare a pointer variable of type struct record

   struct record *temp;

   temp = init();

   printf("Default record\n Roll = %d\n Marks = %f\n Name = %s", temp.roll, temp.marks, temp.str);

   // free the memory used. This frees both the memory blocks allocated in init() method.

   // not deleting the memory block might work fine for this method, but will eventually have a memory 

  // leak if a complex program is written which utilizes heavy system resources

   free(temp) 

   return 0;

}

Output:

Default record

Roll = 1;

Marks = 10.000000

Name = default

   

As we saw from the above snippets, returning multiple values from a method is very easy. The structures could be extended to hold as many values as required. And a method return type signature could be used to return the structure type.

Have fun with C!