VariantDict

glib.VariantDict is a mutable interface to glib.Variant dictionaries.

It can be used for doing a sequence of dictionary lookups in an efficient way on an existing glib.Variant dictionary or it can be used to construct new dictionaries with a hashtable-like interface. It can also be used for taking existing dictionaries and modifying them in order to create new ones.

glib.VariantDict can only be used with G_VARIANT_TYPE_VARDICT dictionaries.

It is possible to use glib.VariantDict allocated on the stack or on the heap. When using a stack-allocated glib.VariantDict, you begin with a call to Variant.dictInit and free the resources with a call to Variant.dictClear.

Heap-allocated glib.VariantDict follows normal refcounting rules: you allocate it with Variant.dictNew and use Variant.dictRef and Variant.dictUnref.

Variant.dictEnd is used to convert the glib.VariantDict back into a dictionary-type glib.Variant When used with stack-allocated instances, this also implicitly frees all associated memory, but for heap-allocated instances, you must still call Variant.dictUnref afterwards.

You will typically want to use a heap-allocated glib.VariantDict when you expose it as part of an API. For most other uses, the stack-allocated form will be more convenient.

Consider the following two examples that do the same thing in each style: take an existing dictionary and look up the "count" uint32 key, adding 1 to it if it is found, or returning an error if the key is not found. Each returns the new dictionary as a floating glib.Variant

Using a stack-allocated GVariantDict

GVariant *
add_to_count (GVariant  *orig,
GError   **error)
{
GVariantDict dict;
guint32 count;

g_variant_dict_init (&dict, orig);
if (!g_variant_dict_lookup (&dict, "count", "u", &count))
{
g_set_error (...);
g_variant_dict_clear (&dict);
return NULL;
}

g_variant_dict_insert (&dict, "count", "u", count + 1);

return g_variant_dict_end (&dict);
}

Using heap-allocated GVariantDict

GVariant *
add_to_count (GVariant  *orig,
GError   **error)
{
GVariantDict *dict;
GVariant *result;
guint32 count;

dict = g_variant_dict_new (orig);

if (g_variant_dict_lookup (dict, "count", "u", &count))
{
g_variant_dict_insert (dict, "count", "u", count + 1);
result = g_variant_dict_end (dict);
}
else
{
g_set_error (...);
result = NULL;
}

g_variant_dict_unref (dict);

return result;
}