referencing a structure element from another structure

**ajitht1986** · 02-08-2011

Hello,

This is a working peice of code but couldn't explain how it woks.

Code:

struct stA
{
    ...

    int data;
    ...
    
} ;

struct stB
{
    ...

    int fields;
    struct stA *stA_ptr;

    ...
};

main()
{
    struct stB *stB_ptr;

   // i could see a statement like

   stB_ptr->stA_ptr[8].data=1500;     
  
   ...
}

I'v 2 questions at this point

stA_ptr is just a pointer to structure stA.

1. Then what does stA_ptr[8] imply ?

2. How is it possible to access the element "data" in stA using stA_ptr[8].data ?
I hope "stA_ptr[8]->data" should be the correct form but still its working.

Hope to get a reply soon

**Eman** · 02-08-2011

i think if you declared an array of stA struct objects...
then stA->ptr[8] would be a pointer to the last element, say, if the array size was 9
.. i think

**cph** · 02-08-2011

1. 9th element
2. because stA_ptr is allocated as an array of stA

cmiiw

**Eman** · 02-08-2011

Originally Posted by cph

1. 9th element
2. because stA_ptr is allocated as an array of stA

cmiiw

:S i'm confused..if the size of an array is 9 then last index is SIZE-1..in my example that is why I said 8..

i don't know about number 2. All i can say (guess) is stA_ptr references stA struct object.array or otherwise

**ajitht1986** · 02-08-2011

Thanks Eman & cph.

cph,

Can you plz give further explanation on my 2nd question. I'm not able to follow.

**cph** · 02-08-2011

Originally Posted by ajitht1986

Thanks Eman & cph.

cph,

Can you plz give further explanation on my 2nd question. I'm not able to follow.

Code:

size_t max = 9; /* at least */

stB_ptr->stA_ptr = malloc(max * sizeof(*(stB_ptr->stA_ptr)));

if (stB_ptr->stA_ptr != NULL) {
    printf("Bam! and you have an array of...what?\n");

    /* do something */
    /* something like this?... */
    stB_ptr->stA_ptr[8].data=1500; 

    free(stB_ptr->stA_ptr);
}

probably like that, pcmiiw (p stands for please

)

Thread: referencing a structure element from another structure

Thread Tools

Search Thread

Display

referencing a structure element from another structure

Similar Threads

Adreess of pointed structure element

pthread question how would I init this data structure?

Problem referencing structure elements by pointer

Dynamic Data Structure -- Which one is better?

referencing C structure elements in assembly

Tags for this Thread