C编程：将struct作为参数传递-函数

Question

I am trying Add a new ITEM to GI array, but this doesn't seem to work. I am hitting a brick wall here. Can anyone advise please? I tried passing additem(GI, &Recs, 222) as shown below and updating values:

#include <stdio.h>


   struct Item {
   double value;
   int unitno;
   int isTa;
   int quant;
   int minQuan;
   char name[31];
};

struct Item GI[21] = {
   { 41.4,1275,01,110,12,"Apples" },
   { 52.99,3826,02,220,24,"Melon" },
};
int Recs=20;
void additem(struct Item item[], int *Recs, int unit);
void addtest();


int main ()
{
addtest();
return 0;
}

void addtest() {
additem(GI, &Recs, 222); 
}

void additem(struct Item item[], int *Recs, int value)
{
printf("--== Adding values! ==--\n");
        GI[21].value=44.44;
        GI[21].quant=44;
        GI[21].minQuan=4;
        strcpy(Recs->name, "vGrape");
return 0;
}

Answer 1

No, it doesn't work. You can't dynamically add items to an array in c. You need dynamic memory allocation for that, namely malloc() and family.

This is not a trivial matter, you can use malloc() 's sister realloc() to increase the size of a previously allocated portion of memory, but you should be careful not to do it too often because memory allocation is expensive in terms of computational time.

Answer 2

大小为21的数组只能采用索引0-20。