更改包含结构打印的数组的值

Question

I would like to access the name field from the array items and print the name but I am having trouble.

I created a pointer 'L' in callInitialize and set it to the upper struct type List which I named 'studentList'.

int callInitialize () {

/*Initialize a List*/
List studentList;
List *L;
L = &studentList;
Initialize(L);

#ifdef DEBUG
    printf("L->count after function call Initialize = %d\n", L->count);
    printf("L->items[0].name after function call Initialize = %s\n", studentList.items[0].name);
#endif 

return 0;
}

I then called Initialize and tried to set the value to test but this is incorrect.

void Initialize (List *L) {
char test = "I like you";
L->count = 0;
L->items[0].name = test;
}

I am unsure of why L->items[0].name = test; is not appropriate. I am getting an incompatible types error but name is char and test is char?

Also, once I do change that value how would I print that? My thinking was that %s would be correct since the type of the field name is char. Print is above in callIntialize as a debug statement.

My struct declarations:

#define MAXNAMESIZE 20
typedef struct {
char name[MAXNAMESIZE];
int grade;   
} Student;

typedef Student Item;
#define MAXLISTSIZE 4
typedef struct {
Item items[MAXLISTSIZE];
int count;
} List;

Thank you for any help.

Answer 1

String copying in C doesn't work like that. Strings are simply arrays of characters, with a null character as the last element used; so to copy a string you need to copy the individual characters from the source array to the corresponding elements in the destination array. There are library functions for doing this, such as strncpy() .

So you would need to change:

L->items[0].name = test;

..to something like:

strncpy(L->items[0].name,test,MAXNAMESIZE);
L->items[0].name[MAXNAMESIZE - 1] = '\0';

..where the second line just makes sure there's a null character at the end, in case test was longer than MAXNAMESIZE .

If the name member of Student had been declared as a char * and allocated with malloc() , rather than declared as an array of char , the assignment would have worked, but probably not done what you wanted -- it would have changed name to point to the same string as test (not a copy of it) and just discarded the original value, leaking the malloc() ed memory.