Method

GLibVariantIterloop

Declaration

gboolean
g_variant_iter_loop (
  GVariantIter* iter,
  const gchar* format_string,
  ...
)

Description

Gets the next item in the container and unpacks it into the variable argument list according to format_string, returning TRUE.

If no more items remain then FALSE is returned.

On the first call to this function, the pointers appearing on the variable argument list are assumed to point at uninitialised memory. On the second and later calls, it is assumed that the same pointers will be given and that they will point to the memory as set by the previous call to this function. This allows the previous values to be freed, as appropriate.

This function is intended to be used with a while loop as demonstrated in the following example. This function can only be used when iterating over an array. It is only valid to call this function with a string constant for the format string and the same string constant must be used each time. Mixing calls to this function and g_variant_iter_next() or g_variant_iter_next_value() on the same iterator causes undefined behavior.

If you break out of a such a while loop using g_variant_iter_loop() then you must free or unreference all the unpacked values as you would with g_variant_get(). Failure to do so will cause a memory leak.

Here is an example for memory management with g_variant_iter_loop():

  // Iterates a dictionary of type 'a{sv}'
  void
  iterate_dictionary (GVariant *dictionary)
  {
    GVariantIter iter;
    GVariant *value;
    gchar *key;

    g_variant_iter_init (&iter, dictionary);
    while (g_variant_iter_loop (&iter, "{sv}", &key, &value))
      {
        g_print ("Item '%s' has type '%s'\n", key,
                 g_variant_get_type_string (value));

        // no need to free 'key' and 'value' here
        // unless breaking out of this loop
      }
  }

For most cases you should use g_variant_iter_next().

This function is really only useful when unpacking into GVariant or GVariantIter in order to allow you to skip the call to g_variant_unref() or g_variant_iter_free().

For example, if you are only looping over simple integer and string types, g_variant_iter_next() is definitely preferred. For string types, use the ‘&’ prefix to avoid allocating any memory at all (and thereby avoiding the need to free anything as well).

format_string determines the C types that are used for unpacking the values and also determines if the values are copied or borrowed.

See the section on [GVariant format strings][gvariant-format-strings-pointers].

Available since:2.24
This method is not directly available to language bindings.

Parameters

format_string

Type: const gchar*

A GVariant format string.

The data is owned by the caller of the function.
The value is a NUL terminated UTF-8 string.
...

Type: 

The arguments to unpack the value into.

Return value

Type: gboolean

TRUE if a value was unpacked, or FALSE if there was no value.