glib:variant-type-first (vtype)

vtype -- a tuple or dictionary entry g:variant-type instance

The g:variant-type instance with the first item type of vtype.

Determines the first item type of a tuple or dictionary entry type. This function may only be used with tuple or dictionary entry types, but must not be used with the generic r tuple type. In the case of a dictionary entry type, this returns the type of the key. The nil value is returned in case of type being the "()" type string. This call, together with the g:variant-type-next function provides an iterator interface over tuple and dictionary entry types.