Types of possible errors as a result of requesting a value from the session storage

Stores a value inside the session:

action SessionExampleAction { userId } = do
    setSession "userId" userId

For cases where setSession is used with literals, to avoid type ambiguity, you can use one of the options below

Example: Annotate a literal with a type

action LogoutAction = do
    setSession "userEmail" ("hi@digitallyinduced.com" :: Text)

Example: Using setSession with type application

action LogoutAction = do
    setSession @Text "userEmail" "hi@digitallyinduced.com"

Retrives a value from the session:

action SessionExampleAction = do
    userEmail <- getSession @Text "userEmail"
    counter <- getSession @Int "counter"
    userId <- getSession @(Id User) "userId"

userEmail is set to Just' "hidigitallyinduced.com"@ when the value has been set before. Otherwise, it will be Nothing.

If an error occurs while getting the value, the result will be Nothing.

Retrives a value from the session:

getSession variant, which returns SessionError if an error occurs while getting value from session storage

action SessionExampleAction = do
    counter <- getSessionEither @Int "counter"
    case counter of
        Right value -> ...
        Left (ParseError errorMessage) -> ...
        Left NotFoundError -> ...
        Left VaultError -> ...

Remove session values from storage:

Example: Deleting a userId field from the session

action LogoutAction = do
    deleteSession "userId"

Example: Calling getSession after using deleteSession will return Nothing

setSession "userId" (1337 :: Int)
userId <- getSession @Int "userId" -- Returns: Just 1337

deleteSession "userId"
userId <- getSession @Int "userId" -- Returns: Nothing

Returns a value from the session, and deletes it after retrieving:

action SessionExampleAction = do
    notification <- getSessionAndClear @Text "notification"