gobject的g_object_new_with_properties使用示例

g_object_new_with_properties 是一个创建 GObject 对象的函数，它可以使用属性列表来设置对象的属性。以下是一个示例：

#include <glib-object.h>

typedef struct _MyObject MyObject;

struct _MyObject {
  GObject parent_instance;
  gint    int_prop;
  gchar*  string_prop;
};

enum {
  PROP_INT_PROP = 1,
  PROP_STRING_PROP,
  N_PROPERTIES
};

static GParamSpec* obj_properties[N_PROPERTIES] = { NULL, };

static void my_object_set_property(GObject* object, guint prop_id, const GValue* value, GParamSpec* pspec)
{
  MyObject* self = MY_OBJECT(object);

  switch (prop_id) {
    case PROP_INT_PROP:
      self->int_prop = g_value_get_int(value);
      break;

    case PROP_STRING_PROP:
      g_free(self->string_prop);
      self->string_prop = g_strdup(g_value_get_string(value));
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
      break;
  }
}

static void my_object_get_property(GObject* object, guint prop_id, GValue* value, GParamSpec* pspec)
{
  MyObject* self = MY_OBJECT(object);

  switch (prop_id) {
    case PROP_INT_PROP:
      g_value_set_int(value, self->int_prop);
      break;

    case PROP_STRING_PROP:
      g_value_set_string(value, self->string_prop);
      break;

    default:
      G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
      break;
  }
}

static void my_object_class_init(MyObjectClass* klass)
{
  GObjectClass* object_class = G_OBJECT_CLASS(klass);

  object_class->set_property = my_object_set_property;
  object_class->get_property = my_object_get_property;

  obj_properties[PROP_INT_PROP] = g_param_spec_int("int-prop",
                                                    "Int property",
                                                    "An integer property",
                                                    G_MININT,
                                                    G_MAXINT,
                                                    0,
                                                    G_PARAM_READWRITE);

  obj_properties[PROP_STRING_PROP] = g_param_spec_string("string-prop",
                                                          "String property",
                                                          "A string property",
                                                          "",
                                                          G_PARAM_READWRITE);

  g_object_class_install_properties(object_class, N_PROPERTIES, obj_properties);
}

static void my_object_init(MyObject* self)
{
  self->int_prop = 0;
  self->string_prop = g_strdup("");
}

int main(int argc, char** argv)
{
  g_type_init();

  MyObject* obj = g_object_new_with_properties(MY_TYPE_OBJECT,
                                                "int-prop", 42,
                                                "string-prop", "Hello, world!",
                                                NULL);

  g_object_unref(obj);

  return 0;
}

这个示例定义了一个名为 MyObject 的 GObject 子类，它包含一个整数属性 int_prop 和一个字符串属性 string_prop。在 my_object_class_init 函数中，我们使用 g_param_spec_int 和 g_param_spec_string 函数来定义这些属性的参数规范。然后，我们使用 g_object_class_install_properties 将这些属性添加到对象类中。

在 my_object_set_property 和 my_object_get_property 函数中，我们实现了属性的设置和获取方法。在 main 函数中，我们使用 g_object_new_with_properties 函数创建一个 MyObject 实例，并设置 int_prop 和 string_prop 属性的值。最后，我们必须调用 g_object_unref 函数来释放对象的引用。