Thread: how do i create an array...

how do i a function to create an array of n amount of structures dynamically and then to return a pointer to array. So far I have ....

Code:

typedef struct{
	char *name;
	int day_of_birth;
	int month_of_birth;
	int year_of_birth;
} data_t;


data_t
create_data_t_array(int n) {
	int i;
	data_t *ptr;
	ptr = malloc(sizeof(*ptr));
	for (i = 0; i < n; i++)
	{
	ptr[i] = malloc(sizeof(*ptr))	
	}
	return ptr;		 
}

but i dont think will work. pls help!

You nearly had the correct solution:

1. First of all, your function shouldn't return a data_t but instead a pointer to data_t
2. The way you're allocating your array inside the function is wrong. Just do it like you would do for integers:

Code:

int *array = malloc(100 * sizeof(*array));

The code you want is the following:

Code:

data_t *create_data_t_array(int n) {
	data_t *ptr;
	ptr = malloc(n * sizeof(*ptr));
	return ptr;
}

int main(void)
{
  data_t *myArray = create_data_t_array(10);
  return 0;
}

should I also have to initialize it first :

Code:

void
init_array (data_t *pt_arrayr, int n) {
	int i;
	for (i = 0; i < n; i++)
	{
		ptr_array[i].name = {0};
		ptr_array[i].day_of_birth = 0;
		ptr_array[i].month_of_birth = 0;
		ptr_array[i].year_of_birth = 0;
	}
}

is this nessecary?

what would you recommend a as a good way to take input from keystroke. I have started writing a read_into_function but am having trouble formulating a loop system for it to iterate through each element, and then to the next structure in the array etc etc

I tried ptr_array[i] = NULL, I had to define NULL as 0 and then the compiler didn't like it :

c:34: error: incompatible types in assignment ?

I want to pass information into members of the array of structures. I know the number of structure, n, and I have a pointer to the array. I want to step through each member of structure collecting the fields and then I want to move on to the next structure in the array.

something like this, but im not sure how to walk though each member of each structure within the array. I though about using an if(ch=="\n"), then iterate, but how do iterate the pointer, like this : ptr_array++?

Code:

data_t 
read_into_array(bday_t *ptr_array, int n) {
		int next;
		printf("Enter a name, date of birth, month of birth, and year of birth: \n");
		
		values_read = scanf("%s %d %d %d", ptr_array->name, &(ptr_array->day_of_birth), &(ptr_array->month_of_birth, &(ptr_array->year_of_birth));