access value in struct through pointer to struct

Question

I have a struct:

struct example {
    char arr[SIZE];
    char arr2[SIZE];
};

Then I have a function that has as parameter, pointer to some defined struct example. How do I access the values for its arr and arr2?

void someFunction (const void *ptr1) {

    struct example firstStruct = ...

    /* I want to access firstStruct.arr, firstStruct.arr2 somewhere here */

}

Answer 1

You could do something like this:

struct example *exPtr = (struct example*) ptr1;

And then, to access a specific member in the struct, just use the dereference operator (->). For instance,

printf("arr = %s\\narr2 = %s", exPtr->arr, exPtr->arr2)

Answer 2

You have two options.

• Cast the void pointer:

   void somefunction(const void* ptr1){ struct example* firstStruct = (struct example*) ptr1; char c; // some access to array inside struct c = firstStruct->arr[0]; } 

• Pass pointer to struct as a parameter:

   void somefunction(struct example* ptr1){ char c; // just use the "->" operator c = ptr1->arr[0]; }