storr for fetching external resources. This driver is used where
will try to fetch from an external data source if a resource can
not be found locally. This works by checking to see if a key is
present in the storr (and if so returning it). If it is not
found, then the function fetch_hook is run to fetch it.
storr_external(storage_driver, fetch_hook, default_namespace = "objects")Another storr driver to handle the
actual storage.
A function to run to fetch data when a key is
not found in the store. This function must take arguments
key and namespace and return an R object. It must
throw an error if the external resource cannot be resolved.
Default namespace (see
storr)
See the vignette vignette("external") for much more detail.
This function is likely most useful for things like caching
resources from websites, or computing long-running quantities on
demand.