R: Set and Retrieve Store Contents

set_unitizer {unitizer}

R Documentation

Set and Retrieve Store Contents

Description

These functions are not used directly; rather, they are used by unitize to get and set the unitizer objects. You should only need to understand these functions if you are looking to implement a special storage mechanism for the unitizer objects.

Usage

set_unitizer(store.id, unitizer)

get_unitizer(store.id)

## S3 method for class 'character'
get_unitizer(store.id)

## Default S3 method:
get_unitizer(store.id)

## S3 method for class 'unitizer_result'
get_unitizer(store.id)

## S3 method for class 'unitizer_results'
get_unitizer(store.id)

Arguments

`store.id`	a filesystem path to the store (an .rds file)
`unitizer`	a `unitizer-class` object containing the store data

Details

By default, only a character method is defined, which will interpret its inputs as a filesystem path to the unitizer folder. RDSes of serialization type 2 will be stored and retrieved from there. The serialization format may change in the future, but if R maintains facilities to read/write type 2, we will provide the option to use that format. At this time there is no API to change the serialization format.

You may write your own methods for special storage situations ( e.g SQL database, ftp server, etc) with the understanding that the getting method may only accept one argument, the store.id, and the setting method only two arguments, the store.id and the unitizer.

S3 dispatch will be on store.id, and store.id may be any R object that identifies the unitizer. For example, a potential SQL implementation where the unitizers get stored in blobs may look like so:

my.sql.store.id <- structure(
  list(
    server="myunitizerserver.mydomain.com:3306",
    database="unitizers",
    table="project1",
    id="cornercasetests"
  ),
  class="sql_unitizer"
)
get_unitizer.sql_unitizer <- function(store.id) { # FUNCTION BODY }
set_unitizer.sql_unitizer <- function(store.id, unitizer) { # FUNCTION BODY }

unitize("unitizer/cornertestcases.R", my.sql.store.id)

Make sure you also define an as.character method for your object to produce a human readable identifying string.

For inspirations for the bodies of the _store functions look at the source code for unitizer:::get_unitizer.character and unitizer:::set_unitizer.character. Expectations for the functions are as follows. get_unitizer must:

return a unitizer-class object if store.id exists and contains a valid object
return FALSE if the object doesn't exist (e.g. first time run-through, so reference copy doesn't exist yet)
stop on error

set_unitizer must:

return TRUE on success
stop on error

Value