Access JS webstorage (local & session) in a type-safe and convenient way. Just define a key type with some smart constructors and you are done (GADTs would even make those unnecessary).
The type system then saves you from misspelling keys (no plain strings) and also makes sure that you can only read the same type as you wrote before. This is because the keys encode the type of the data stored with them in the type system.
In addition to type safety, having a key type instead of plain strings
also makes the API easier to use, because with the value type encoded
in the key type, type inference is always possible, even for a plain
getItem call. You will never need any type annotations!
The values you want to store should have a Generic instance, then
everything just works. Alternatively, if your type is not Generic, you can provide
EncodeJson and DecodeJson instances and use getItem, setItem and friends
from DOM.WebStorage.JSON.
Find a basic usage example in test/Example.purs, repeated here for convenience:
module Example.Main where
import Prelude
import Control.Monad.Eff (Eff)
import Control.Monad.Eff.Console (CONSOLE, log)
import Data.Generic (class Generic, gShow)
import Data.Maybe (maybe)
import DOM (DOM)
import DOM.WebStorage (STORAGE, getItem, setItem, getLocalStorage)
-- 1. Define item types to store.
newtype UserConfig = UserConfig { name :: String, email :: String }
-- TODO: manually implement codecs formatted as "name <email>".
derive instance genericUserConfig :: Generic UserConfig
newtype ServerCache = ServerCache { lastModified :: Number, recentContacts :: Array UserConfig }
-- 2. Either implement EncodeJson and DecodeJson or derive Generic for (de)serialization.
derive instance genericServerCache :: Generic ServerCache
-- 3. Define keys as a "phantom type".
data ExampleKey a = UserConfigKey
| ServerCacheKey
derive instance genericExampleKey :: Generic (ExampleKey a)
-- 4. Make "smart constructor" for each key.
userConfigKey :: ExampleKey UserConfig
userConfigKey = UserConfigKey
serverCacheKey :: ExampleKey ServerCache
serverCacheKey = ServerCacheKey
{- 5. Optionally ask the tooth fairy for a GADT under your pillow.
data ExampleKey a where
UserConfig :: ExampleKey UserConfig
ServerCache :: ExampleKey ServerCache
-}
-- 6. Run in browser.
main :: Eff (console :: CONSOLE, storage :: STORAGE, dom :: DOM) Unit
main = do
let userConfig = UserConfig { name : "PureScript", email : "[email protected]" }
localStorage <- getLocalStorage
setItem localStorage userConfigKey userConfig
result <- getItem localStorage userConfigKey
log $ maybe "Are you Private Browsing in Safari?" gShow resultHave fun!
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