Initializing a certain struct field on-initialization in C

Question

What I would like to do here is initializing all the players' names with the empty string value "", I have heard it can be done at the declaration point in C99, but I'm not entirely sure how.

typedef struct data_players
{   char name[25];
    int hp;
    int mana;
    int id;

}player;

player player_list[10]

In this case how should I proceed?

You are editing the question, making answers invalid. Not a good thing to do here. — Imobilis
– Imobilis, Commented May 12, 2015 at 17:23
I know, I forgot an rather important aspect of the question, apologies. — Zetsuno
– Zetsuno, Commented May 12, 2015 at 17:25

Imobilis · Accepted Answer · 2015-06-26 04:10:11Z

3

struct data_players
{   char name[25];

} player = "";

or

struct data_players
{   char name[25];

} player = { "" };

This initializes the first member of the structure at declaration time. If there are more members, separate them with comma. One more thing. Your struct should not be type-defined at declaration time to do that kind of initialization.

if you have an array of structures and you want to initialize them in C99 you can use "designated initializer" at declaration time.

player arr [2] = { {.name = ""}, {.name = ""} };

This will initialize arr[0] and arr[1]'s name members to a null string. Though I see not much sense in it as it defaults to a null string anyway.

edited Jun 26, 2015 at 4:10

answered May 12, 2015 at 17:20

Imobilis

1,4999 silver badges29 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Zetsuno Over a year ago

Hm, perhaps my example wasn't that good, because there are multiple fields in the struct, not only the name, in that case, how would that be? sorry for the misunderstanding.

Imobilis Over a year ago

@Zetsuno I see now you've accepted mtijanic's offering. Good thing it helped.. though his solution is not C99 specific but C89 specific. The designated initializer I provided not only is C99 specific but also a better way of initialization (: Take this into a consideration.

mtijanic · Accepted Answer · 2015-05-12 19:16:52Z

2

At declaration time, you initialize structs with {} like this:

player player_list[10] = {{"", 0, 0, 0},{"", 0, 0, 0},{"", 0, 0, 0},{"", 0, 0, 0},{"", 0, 0, 0},{"", 0, 0, 0},{"", 0, 0, 0},{"", 0, 0, 0},{"", 0, 0, 0},{"", 0, 0, 0}};

Note that any skipped initializers will default to zero, so if you are always initializing the entire array to zero, this will suffice:

player player_list[10] = {0};

Also note that if player_list is a global or a static variable, it will automatically be initialized to all zeroes. As if you called

memset(player_list, 0, sizeof(player_list));

at program start.

edited May 12, 2015 at 19:16

answered May 12, 2015 at 17:22

mtijanic

2,91214 silver badges27 bronze badges

2 Comments

Zetsuno Over a year ago

Thanks a lot, this did solve my problem, since it dosn't really matter if I initialize everything to zero, in my case.

cremno Over a year ago

player player_list[10] = {}; is using a GNU C extension. {0} is the ISO C way.

Collectives™ on Stack Overflow

Initializing a certain struct field on-initialization in C

2 Answers 2

2 Comments

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

2 Comments

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related