gio:action-state-type (object)

object -- a g:action object
vtype -- a g:variant-type parameter type, for the state type if the action is stateful

Accessor of the state-type slot of the action class. Queries the type of the state of the action. If the action is stateful, for example created with the g:simple-action-new-stateful function, then this function returns the g:variant-type parameter type of the state. This is the type of the initial value given as the state. All calls to the g:action-change-state function must give a g:variant parameter of this type and the g:action-state function will return a g:variant parameter of the same type.

If the action is not stateful, for example created with the g:simple-action-new function, then this function will return nil. In that case, the g:action-state function will return a cffi:null-pointer value and you must not call the g:action-change-state function.