自学教程：C++ G_IS_VALUE函数代码示例

gboolean_midgard_dbobject_get_property (MidgardDBObject *self, const gchar *name, GValue *value){	g_return_val_if_fail (self != NULL, FALSE);	g_return_val_if_fail (name != NULL, FALSE);	g_return_val_if_fail (G_IS_VALUE (value), FALSE);	if (!self->dbpriv->datamodel)		return FALSE;	GdaDataModel *model = GDA_DATA_MODEL (self->dbpriv->datamodel);	if (!model || (model && !GDA_IS_DATA_MODEL (model)))		return FALSE;	gint col_idx = gda_data_model_get_column_index (model, name);	if (col_idx == -1)		return FALSE;	const GValue *src_val = gda_data_model_get_value_at (model, col_idx, self->dbpriv->row, NULL);	if (!src_val)		return FALSE;	if (!G_IS_VALUE (src_val) 			|| (G_IS_VALUE (src_val) 				&& G_VALUE_TYPE (src_val) == GDA_TYPE_NULL)) {		/* NULL fetched from underlying field */		if (G_VALUE_HOLDS_STRING (value)) {			g_value_set_string (value, "");			return TRUE;		}		g_warning ("Can not find value for given '%s' property /n", name);		return FALSE;	}	if (G_VALUE_TYPE (src_val) != G_VALUE_TYPE (value))		g_value_transform (src_val, value);	else 		g_value_copy (src_val, value);	if (G_VALUE_HOLDS_STRING (value) && g_value_get_string (value) == NULL)		g_value_set_string (value, "");	return TRUE;}

static voiddestroy_gvalue(GValue *value){	if (value != NULL)	{		g_return_if_fail(G_IS_VALUE(value));		g_value_reset(value);		g_free(value);	}}

gchar *GstUtils::gvalue_serialize(const GValue *val) {  if (!G_IS_VALUE(val))    return nullptr;  gchar *val_str;  if (G_VALUE_TYPE(val) == G_TYPE_STRING)    val_str = g_strdup(g_value_get_string(val));  else    val_str = gst_value_serialize(val);  return val_str;}

coil_expandable_value_equals(const GValue  *v1,                             const GValue  *v2,                             GError       **error) /* no need */{  g_return_val_if_fail(G_IS_VALUE(v1), FALSE);  g_return_val_if_fail(G_IS_VALUE(v2), FALSE);  g_return_val_if_fail(error == NULL || *error == NULL, FALSE);  const CoilExpandable *x1, *x2;  if (!(G_VALUE_HOLDS(v1, COIL_TYPE_EXPANDABLE)    && G_VALUE_HOLDS(v2, COIL_TYPE_EXPANDABLE)))    return FALSE;  x1 = COIL_EXPANDABLE(g_value_get_object(v1));  x2 = COIL_EXPANDABLE(g_value_get_object(v2));  return coil_expandable_equals(x1, x2, error);}

const gchar *conting_attributes_get_string(ContingAttributes *self, const gchar *name){    const GValue *value;    value = conting_attributes_get_value(self, name);    g_return_val_if_fail(value != NULL && G_IS_VALUE(value), NULL);    return g_value_get_string(value);}

static voidgst_lfo_control_source_reset (GstLFOControlSource * self){  GstControlSource *csource = GST_CONTROL_SOURCE (self);  csource->get_value = NULL;  csource->get_value_array = NULL;  self->priv->type = self->priv->base = G_TYPE_INVALID;  if (G_IS_VALUE (&self->priv->minimum_value))    g_value_unset (&self->priv->minimum_value);  if (G_IS_VALUE (&self->priv->maximum_value))    g_value_unset (&self->priv->maximum_value);  if (G_IS_VALUE (&self->priv->amplitude))    g_value_unset (&self->priv->amplitude);  if (G_IS_VALUE (&self->priv->offset))    g_value_unset (&self->priv->offset);}

static voidvalue_free (GDataFreebaseTopicValue *value){	if (G_IS_VALUE (&value->value))		g_value_unset (&value->value);	g_free (value->text);	g_free (value->lang);	g_free (value->creator);	g_free (value->property);	g_slice_free (GDataFreebaseTopicValue, value);}

static VALUEgobj_new_ensure(struct param_setup_arg* arg){    guint i;    g_type_class_unref(arg->gclass);    for (i = 0; i < arg->param_size; i++) {        if (G_IS_VALUE(&arg->params[i].value))            g_value_unset(&arg->params[i].value);    }    return Qnil;}

/** * g_value_fits_pointer: * @value: An initialized #GValue structure. * * Determines if @value will fit inside the size of a pointer value. * This is an internal function introduced mainly for C marshallers. * * Returns: %TRUE if @value will fit inside a pointer value. */gbooleang_value_fits_pointer (const GValue *value){    GTypeValueTable *value_table;    g_return_val_if_fail (G_IS_VALUE (value), FALSE);    value_table = g_type_value_table_peek (G_VALUE_TYPE (value));    return value_table->value_peek_pointer != NULL;}

gboolean property_context_from_gvalue(PropertyContext * ctx, GValue * value){    if (ctx == NULL) {        return FALSE;    }    if (!G_IS_VALUE(value)) {        return FALSE;    }    g_value_copy(value, &(ctx->value));    return TRUE;}

static voidfinalize (GObject *object){	NMVPNPlugin *plugin = NM_VPN_PLUGIN (object);	NMVPNPluginPrivate *priv = NM_VPN_PLUGIN_GET_PRIVATE (plugin);	nm_vpn_plugin_set_connection (plugin, NULL);	g_free (priv->dbus_service_name);	if (G_IS_VALUE (&priv->banner))		g_value_unset (&priv->banner);	if (G_IS_VALUE (&priv->tundev))		g_value_unset (&priv->tundev);	if (G_IS_VALUE (&priv->gateway))		g_value_unset (&priv->gateway);	if (G_IS_VALUE (&priv->mtu))		g_value_unset (&priv->mtu);	G_OBJECT_CLASS (nm_vpn_plugin_parent_class)->finalize (object);}

static SteadyflowCoreIDownloadFile* steadyflow_file_list_controller_file_from_iter (SteadyflowFileListController* self, GtkTreeIter* iter) {	SteadyflowCoreIDownloadFile* result = NULL;	GValue value = {0};	GtkListStore* _tmp0_;	GtkTreeIter _tmp1_;	GValue _tmp2_ = {0};	GObject* _tmp3_ = NULL;	SteadyflowCoreIDownloadFile* _tmp4_;	g_return_val_if_fail (self != NULL, NULL);	g_return_val_if_fail (iter != NULL, NULL);	_tmp0_ = self->priv->model;	_tmp1_ = *iter;	gtk_tree_model_get_value ((GtkTreeModel*) _tmp0_, &_tmp1_, 0, &_tmp2_);	G_IS_VALUE (&value) ? (g_value_unset (&value), NULL) : NULL;	value = _tmp2_;	_tmp3_ = g_value_get_object (&value);	_tmp4_ = _g_object_ref0 (STEADYFLOW_CORE_IDOWNLOAD_FILE (_tmp3_));	result = _tmp4_;	G_IS_VALUE (&value) ? (g_value_unset (&value), NULL) : NULL;	return result;}

static GValue *test_gvalue_callback (GObject *object, const GValue *v){  GValue *ret = g_malloc0 (sizeof (GValue));  g_return_val_if_fail (G_IS_OBJECT (object), NULL);  g_return_val_if_fail (G_IS_VALUE (v), NULL);  g_value_init (ret, G_VALUE_TYPE (v));  g_value_copy (v, ret);  return ret;}

/** * gnc_value_get_guid * * @param value a @c GValue whose value we want to get. * * @return the value stored in @a value */const GncGUID*gnc_value_get_guid (const GValue *value){    GncGUID *val;    g_return_val_if_fail (value && G_IS_VALUE (value), NULL);    g_return_val_if_fail (GNC_VALUE_HOLDS_GUID (value), NULL);    val = (GncGUID*) g_value_get_boxed (value);    return val;}

gboolean GN_value_unset(int ARI, ei_x_buff *XBUF, char *B, int *I){  GValue* object;  /* no return value */  if ( ! gn_check_arity(XBUF, 1, ARI) ) return FALSE;  if ( ! gn_get_arg_struct(XBUF, B, I, "GValue", (void**)&object) ) return FALSE;  if ( G_IS_VALUE(object) ) g_value_unset(object);  gn_put_void(XBUF);  return TRUE;}

static VALUErbgio_gasyncinitable_new_async_ensure(struct rbgio_gasyncinitable_new_async_data *data){        guint i;        g_type_class_unref(data->gclass);        for (i = 0; i < data->n_parameters; i++)                if (G_IS_VALUE(&data->parameters[i].value))                        g_value_unset(&data->parameters[i].value);        return Qnil;}

static voidupdate_type_list (AnjutaShell *shell, IAnjutaIterable *iter, const gchar *name){	gchar *list = NULL;	GValue value = {0,};		if (iter)	{		ianjuta_iterable_first (iter, NULL);		if (ianjuta_iterable_get_length (iter, NULL) > 0)		{			GString *s = g_string_sized_new(ianjuta_iterable_get_length (iter, NULL) * 10);			do {				IAnjutaSymbol *symbol = IANJUTA_SYMBOL (iter);				const gchar *sname = ianjuta_symbol_get_string (symbol, IANJUTA_SYMBOL_FIELD_NAME, NULL);				g_string_append(s, sname);				g_string_append_c(s, ' ');			} while (ianjuta_iterable_next (iter, NULL));			list =  g_string_free(s, FALSE);		}	}		anjuta_shell_get_value (shell, name, &value, NULL);	if (G_VALUE_HOLDS_STRING(&value))	{		const gchar *value_list = g_value_get_string (&value);				if (list == NULL)		{			anjuta_shell_remove_value (shell, name, NULL);		}		else if (strcmp (list, value_list) == 0)		{			g_free (list);		}		else		{			g_value_take_string (&value, list);			anjuta_shell_add_value (shell, name, &value, NULL);		}	}	else	{		if (list != NULL)		{			g_value_init (&value, G_TYPE_STRING);			g_value_take_string (&value, list);			anjuta_shell_add_value (shell, name, &value, NULL);		}	}	if (G_IS_VALUE (&value))		g_value_unset (&value);}

static void_midgard_cr_core_query_value_finalize (GObject *object){	MidgardCRCoreQueryValue *self = MIDGARD_CR_CORE_QUERY_VALUE (object);	if (G_IS_VALUE (&self->priv->value))		g_value_unset (&self->priv->value);	g_free (self->priv);	self->priv = NULL;	parent_class->finalize (object);}

/** * g_value_unset: * @value: An initialized #GValue structure. * * Clears the current value in @value and "unsets" the type, * this releases all resources associated with this GValue. * An unset value is the same as an uninitialized (zero-filled) * #GValue structure. */voidg_value_unset (GValue *value){    GTypeValueTable *value_table;    g_return_if_fail (G_IS_VALUE (value));    value_table = g_type_value_table_peek (G_VALUE_TYPE (value));    if (value_table->value_free)        value_table->value_free (value);    memset (value, 0, sizeof (*value));}

/** * g_value_copy: * @src_value: An initialized #GValue structure. * @dest_value: An initialized #GValue structure of the same type as @src_value. * * Copies the value of @src_value into @dest_value. */voidg_value_copy (const GValue *src_value,              GValue       *dest_value){    g_return_if_fail (G_IS_VALUE (src_value));    g_return_if_fail (G_IS_VALUE (dest_value));    g_return_if_fail (g_value_type_compatible (G_VALUE_TYPE (src_value), G_VALUE_TYPE (dest_value)));    if (src_value != dest_value)    {        GType dest_type = G_VALUE_TYPE (dest_value);        GTypeValueTable *value_table = g_type_value_table_peek (dest_type);        /* make sure dest_value's value is free()d */        if (value_table->value_free)            value_table->value_free (dest_value);        /* setup and copy */        value_meminit (dest_value, dest_type);        value_table->value_copy (src_value, dest_value);    }}

static voidproperty_hash_recover  (gpointer key,			gpointer value,			gpointer user_data){	PropertyCmdRemove *cmd = (PropertyCmdRemove*) user_data;	g_assert (MRP_IS_TASK (key) || MRP_IS_RESOURCE (key));	g_assert (G_IS_VALUE (value));	mrp_object_set_property (key, cmd->property, value);}

static void_midgard_query_property_finalize (GObject *object){	MidgardQueryProperty *self = MIDGARD_QUERY_PROPERTY (object);	if (self->priv && G_IS_VALUE (&self->priv->value))		g_value_unset (&self->priv->value);	g_free (self->priv);	self->priv = NULL;        parent_class->finalize (object);}

/** * goo_canvas_item_model_set_child_property: * @model: a #GooCanvasItemModel. * @child: a child #GooCanvasItemModel. * @property_name: the name of the child property to set. * @value: the value to set the property to. *  * Sets a child property of @child. **/voidgoo_canvas_item_model_set_child_property (GooCanvasItemModel *model,					  GooCanvasItemModel *child,					  const gchar        *property_name,					  const GValue       *value){  g_return_if_fail (GOO_IS_CANVAS_ITEM_MODEL (model));  g_return_if_fail (GOO_IS_CANVAS_ITEM_MODEL (child));  g_return_if_fail (property_name != NULL);  g_return_if_fail (G_IS_VALUE (value));  _goo_canvas_item_set_child_property_internal ((GObject*) model, (GObject*) child, property_name, value, _goo_canvas_item_model_child_property_pool, _goo_canvas_item_model_child_property_notify_context, TRUE);}

static intgvalue_free( im_object obj ){	GValue *value = obj;	/* If it's just zeros (built but not used) we'll get an error if we	 * unset().	 */	if( G_IS_VALUE( value ) )		g_value_unset( value );	return( 0 );}

static voidgwy_data_view_get_property(GObject *object,                           guint prop_id,                           GValue *value,                           GParamSpec *pspec){    switch (prop_id) {        default:        G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);        break;    }    g_assert(G_IS_VALUE(value));}

coil_expand_value(const GValue  *value,                  const GValue **return_value,                  gboolean       recursive,                  GError       **error){  g_return_val_if_fail(G_IS_VALUE(value), FALSE);  g_return_val_if_fail(G_VALUE_HOLDS(value, COIL_TYPE_EXPANDABLE), FALSE);  g_return_val_if_fail(error == NULL || *error == NULL, FALSE);  CoilExpandable *object = COIL_EXPANDABLE(g_value_get_object(value));  return coil_expand(object, return_value, recursive, error);}

voidon_metadata_edited (GtkCellRendererText *renderer, gchar *path, gchar *new_text, gpointer user_data) {    GtkListStore *store = GTK_LIST_STORE (user_data);    GtkTreePath *treepath = gtk_tree_path_new_from_string (path);    GtkTreeIter iter;    if (!treepath) {        return;    }    gboolean valid = gtk_tree_model_get_iter (GTK_TREE_MODEL (store), &iter, treepath);    gtk_tree_path_free (treepath);    if (!valid) {        return;    }    GValue value = {0,};    GValue mult = {0,};    gtk_tree_model_get_value (GTK_TREE_MODEL (store), &iter, 4, &value);    gtk_tree_model_get_value (GTK_TREE_MODEL (store), &iter, 3, &mult);    const char *svalue = g_value_get_string (&value);    if (!svalue) {        svalue = "";    }    // The multiple values case gets cleared on attempt to edit,    // that's why the change gets applied unconditionally for multivalue case    int imult = g_value_get_int (&mult);    if (strcmp (svalue, new_text) || imult) {        update_meta_iter_with_edited_value (&iter, new_text);        trkproperties_modified = 1;    }    G_IS_VALUE (&value) ? (g_value_unset (&value), NULL) : NULL;    G_IS_VALUE (&mult) ? (g_value_unset (&mult), NULL) : NULL;    trkproperties_block_keyhandler = 0;}