在struct上赋值的类型不兼容

Question

typedef struct s {
char name[20];
char last_name[20];
int height;
} s_t;

s_t my_s_t;
my_s_t.name = "John";

I get "Incompatible types in assignment" for the last line. What am I doing wrong?

Answer 1

my_s_t.name = "John";

name is a char array. So you can´t directly assign a string literal to it. You can use strcpy or similar function to copy the string literal OR declare name as char* .

Options:

1)

typedef struct s {
char name[20];
char last_name[20];
int height;
} s_t;

s_t my_s_t;
strcpy(my_s_t.name, "John");

2)

 typedef struct s {
    char *name;
    char last_name[20];
    int height;
    } s_t;

    s_t my_s_t;
    my_s_t.name = "John";

Answer 2

You are trying to assign an array. Arrays are not assignable. This will fail for the same reason

char a[20];
a = "Hello"; /* Error */

In order to copy data into an array, you have to use a library function, like strcpy

strcpy(a, "Hello");

Meanwhile, it is possible to copy data into an array using core language features (instead of library functions) at the point of initialization , as in

char a[20] = "Hello";

In your case you can use aggregate initialization syntax to achieve the same

s_t my_s_t = { "John", "Smith", 2 };

As long as you are doing this at the point of initialization, it will work. If you have to do it later, then strcpy is your friend.