Re: GList empty after iteration?

[David King <amigadave amigadave com>]

On 2011-09-12 15:10, Craig <craigbakalian verizon net> wrote:
> Hi All,
>
> I am confused about GList. My application is parsing a file and creating
> midi data with it. I am using GList to store the midi data.  I have
> created a GtkListStore to view the parsed data (to insure I am parsing
> the data properly).  So, below I iterate through the GList and "copy"
> the data into a tree view.  But, I am shocked to see that after I
> iterate through the GList, I cannot iterate through the list again.  I
> have debugged the list after the iteration with g_list_length(events)
> which shows the list length at 0.  What is up with this?  The first
> while loop has data, the second while loop has not data. The code is

Another option to those offered in this thread is to use the handy 
g_list_foreach() to iterate over the list.

http://developer.gnome.org/glib/stable/glib-Doubly-Linked-Lists.html#g-list-foreach

This nicely separates out the loop into a function, something like 
(I have not tested this, and it can probably be simplified):

void my_list_foreach_store (gpointer data, gpointer user_data)
{
    GtkTreeIter tree_iter;
    struct midi_event *me = data;
    GtkListStore list_store = GTK_LIST_STORE (user_data);

    gtk_list_store_append (list_store, &tree_iter);
    gtk_list_store_set (list_store, &tree_iter,
                        0, me->time_stamp,
                        1, me->event_type,
                        2, me->message1,
                        3, me->message2,
                       -1);
}

void my_list_foreach_print (gpointer data, gpointer user_data)
{
    g_print ("midi event \n");
}

void a_function ()
{
     GList *events = NULL;
     GtkListStore *store = gtk_list_store_new();

     events = g_list_prepend (events, some_data);
     /* insert more items */

     events = g_list_reverse (events);
     /* No need for g_list_first (), already handled by 
      * g_list_reverse ().

     g_list_foreach (events, my_list_foreach_store, store);
     g_list_foreach (events, my_list_foreach_print, NULL);
}

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