GLib program compile error

Question

I am trying to learn glib programming to see the flow when I create an object using g_object_new() but get this error when I compile, need some tips, what am I doing wrong with G_DEFINE_TYPE (line 25)?

gcc -Wall `pkg-config --cflags --libs glib-2.0` loop.c -o loop
loop.c: In function ‘network_listener_get_type’:
loop.c:25: error: invalid application of ‘sizeof’ to incomplete type ‘NetworkListenerClass’ 
loop.c: In function ‘main’:
loop.c:60: warning: unused variable ‘nl’

The code is:

#include <stdio.h>
#include <glib.h>
#include <glib-object.h>

#define NETWORK_LISTENER_TYPE   (network_listener_get_type())
#define NETWORK_LISTENER(obj)   (G_TYPE_CHECK_INSTANCE_CAST ((obj), NETWORK_LISTENER_TYPE, NetworkListener))

typedef struct _NetworkListener NetworkListener;
typedef struct _NetworkListenerCLass NetworkListenerClass;


 struct _NetworkListener
 {
   GObject parent_instance;
   unsigned int ipAddr;
   int port;
 };

 struct _NetworkListenerClass
 {
   GObjectClass parent_class;
 };

 G_DEFINE_TYPE(NetworkListener, network_listener, G_TYPE_OBJECT);

 static GObject * network_listener_constructor(GType gtype,
                              guint nprops,
                              GObjectConstructParam *props)
 {
    GObject *obj;
    printf("network listener constructor called\n");
    {
      obj = G_OBJECT_CLASS(network_listener_parent_class)->constructor(gtype, nprops, props);
    }
    return obj;
 }

 static void network_listener_class_init(NetworkListenerClass *klass)
 {
   GObjectClass *gobject_class = G_OBJECT_CLASS(klass);
   printf("network listener class init called\n");
   gobject_class->constructor = network_listener_constructor;
 }

 static void network_listener_init(NetworkListener *self)
 {
   printf("Called network_listener_init\n");
                                                                    1,28          Top
 }

 gboolean callback(gpointer data)
 {
   printf("%s\n", (char*)data);
   return TRUE;
 }

 int main()
 {
   GMainLoop* main_loop = NULL;
   NetworkListener *nl = g_object_new(NETWORK_LISTENER_TYPE, NULL);
   main_loop = g_main_loop_new (NULL, FALSE);
/* interval, function callback, userdata */
   g_timeout_add_seconds(10, callback, "callback_function");
   g_main_loop_run(main_loop);
   return 0;
 }

Answer 1

It's a typo in the NetworkListenerClass typedef... there is an uppercase L where there shouldn't be (you have "CLass" instead of "Class").