gobject的g_object_new_with_properties使用实例

g_object_new_with_properties函数可以用于创建一个GObject实例，并且在实例化对象时可以设置该对象的属性值。它的原型如下：

gpointer g_object_new_with_properties (GType object_type,
                                        guint n_properties,
                                        GObjectConstructParam *properties);

其中，object_type是要实例化对象的类型。n_properties是要设置的属性数量。properties是一个GObjectConstructParam类型的数组，用于保存要设置的属性信息。

下面是一个使用g_object_new_with_properties函数创建GObject实例并设置属性的示例代码：

#include <glib-object.h>

typedef struct _MyObject MyObject;

struct _MyObject {
    GObject parent_instance;

    gchar *name;
    gint age;
};

enum {
    PROP_NAME = 1,
    PROP_AGE,
    N_PROPERTIES
};

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

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

    switch (property_id) {
        case PROP_NAME:
            g_free (self->name);
            self->name = g_value_dup_string (value);
            break;
        case PROP_AGE:
            self->age = g_value_get_int (value);
            break;
        default:
            G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
            break;
    }
}

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

    switch (property_id) {
        case PROP_NAME:
            g_value_set_string (value, self->name);
            break;
        case PROP_AGE:
            g_value_set_int (value, self->age);
            break;
        default:
            G_OBJECT_WARN_INVALID_PROPERTY_ID (object, property_id, pspec);
            break;
    }
}

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

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

    obj_properties[PROP_NAME] =
        g_param_spec_string ("name",
                             "Name",
                             "The name of the object",
                             NULL,
                             G_PARAM_READWRITE | G_PARAM_CONSTRUCT);
    obj_properties[PROP_AGE] =
        g_param_spec_int ("age",
                          "Age",
                          "The age of the object",
                          0,
                          G_MAXINT,
                          0,
                          G_PARAM_READWRITE | G_PARAM_CONSTRUCT);

    g_object_class_install_properties (gobject_class,
                                        N_PROPERTIES,
                                        obj_properties);
}

static void my_object_init (MyObject *self)
{
    self->name = NULL;
    self->age = 0;
}

int main (void)
{
    MyObject *obj = g_object_new_with_properties (MY_TYPE_OBJECT,
                                                   2,
                                                   "name", "Tom",
                                                   "age", 18);
    g_object_unref (obj);
    return 0;
}

在上面的示例代码中，我们定义了一个MyObject类型的GObject子类，并且添加了两个属性：name和age。在类初始化时，我们使用g_object_class_install_properties函数将这两个属性安装到MyObject类中。在对象初始化时，我们将这两个属性的默认值分别设置为NULL和0。

在main函数中，我们使用g_object_new_with_properties函数创建一个MyObject实例，并且设置name属性为"Tom"，age属性为18。最后，我们使用g_object_unref函数释放该实例。

需要注意的是，在使用g_object_new_with_properties函数创建对象时，属性名称和属性值必须成对出现，并且属性名称必须是字符串类型。在示例代码中，我们使用"name"和"age"作为属性名称。