Get a value from an object store.

Gets a value, for a given key, from the store.

If there is no coresponding value for the key, then NULL is returned.

# S3 method for class 'object'
storage.get(storage, key)

Arguments

storage

initialized storage

key

key to retrieve value for

Value

Stored value for the key, NULL otherwise.

Examples

library(magrittr)

# initialize default memory storage
my.storage <- storage.init()

# set a value into storage
storage.set(my.storage, "name", "Roy Wetherall")

# .. and some more
my.storage %>% 
  storage.set("age", 45) %>% 
  storage.set("alive", TRUE) %>%
  storage.set("children", c("Peter", "Grace", "Lucy"))

# check a key has been set
if (storage.has(my.storage, "name")) print("I know your name!")
#> [1] "I know your name!"

# .. and that a key hasn't been set
if (!storage.has(my.storage, "address")) print("I don't know where you live!")
#> [1] "I don't know where you live!"

# get some values from storage
sprintf(
  "%s is %i years old.", 
  storage.get(my.storage, "name"),
  storage.get(my.storage, "age"))
#> [1] "Roy Wetherall is 45 years old."

# remove a value from storage
storage.unset(my.storage, "children")

# .. and show it's not there anymore
if (!storage.has(my.storage, "address")) print("I don't know who your children are!")
#> [1] "I don't know who your children are!"

# clear all values from storage
storage.clear(my.storage)

# .. and everything is gone
if (!storage.has(my.storage, "name") && !storage.has(my.storage, "age")) print("I know nothing!")
#> [1] "I know nothing!"

# initialize file storage (direct backend; simplest local-only path)
base.dir <- file.path(tempdir(), "memofunc-storage")
file.storage <- storage.init("file", base.dir = base.dir)

# set and retrieve a value from file storage (direct backend)
storage.set(file.storage, "name", "Roy Wetherall")
storage.get(file.storage, "name")
#> [1] "Roy Wetherall"

# initialize object storage using a provider name (provider-backed interface)
# this uses the same local file backend now, but lets you swap to azure.blob/s3 later
object.storage <- storage.init("object", provider = "file", base.dir = base.dir)
storage.set(object.storage, "name", "Roy Wetherall")
storage.get(object.storage, "name")
#> [1] "Roy Wetherall"

# set a default provider via options
old.options <- options(memofunc.storage.provider = list(name = "file", base.dir = base.dir))
on.exit(options(old.options), add = TRUE)
default.storage <- storage.init()
storage.get(default.storage, "name")
#> NULL

# Azure Blob provider example (requires AzureStor + credentials)
if (requireNamespace("AzureStor", quietly = TRUE)) {
  account <- Sys.getenv("AZURE_STORAGE_ACCOUNT")
  container <- Sys.getenv("AZURE_STORAGE_CONTAINER")
  key <- Sys.getenv("AZURE_STORAGE_KEY")
  token <- Sys.getenv("AZURE_STORAGE_TOKEN")

  if (account != "" && container != "" && (key != "" || token != "")) {
    azure.storage <- storage.init(
      "object",
      provider = "azure.blob",
      account = account,
      container = container,
      key = if (key == "") NULL else key,
      token = if (token == "") NULL else token,
      prefix = "memofunc-example"
    )

    storage.set(azure.storage, "name", "Roy Wetherall")
    storage.get(azure.storage, "name")
  }
}