R: Storr that looks for external resources

storr_external {storr} | R Documentation

## Storr that looks for external resources

### Description

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.

### Usage

    storr_external(storage_driver, fetch_hook, default_namespace = "objects")

### Arguments

`storage_driver` | Another `storr` driver to handle the actual storage.
`fetch_hook` | 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` | Default namespace (see `storr`)

### Details

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.

[Package storr version 1.2.0 Index]