(define-gboxed-opaque variant-dict "GVariantDict"
  :export t
  :type-initializer "g_variant_dict_get_type"
  :alloc (%variant-dict-new (cffi:null-pointer)))  

The g:variant-dict structure is a mutable interface to g:variant dictionaries. It can be used for doing a sequence of dictionary lookups in an efficient way on an existing g: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. The g:variant-dict structure can only be used with a(sv) dictionaries.

You allocate a g:variant-dict instance with the g:variant-dict-new function. The g:variant-dict-end function is used to convert the g:variant-dict instance back into a g:variant dictionary type. This also implicitly frees all associated memory. Using a g:variant-dict instance:

(defun add-to-count (orig)
  (let* ((dict (g:variant-dict-new orig))
         (variant (g:variant-dict-lookup-value dict "count")))
    (when variant
      (let ((value (1+ (g:variant-int32 variant))))
        (g:variant-dict-insert-value dict "count" (g:variant-new-int32 value))
        (g:variant-dict-end dict)))))