from-env

Haskell package to construct datatypes from environment variables.

In many applications you'll have an .env file or set environment variables some way. These environment variables usually contain configuration data such as database connection urls, secrets; etc.

Next, you make a configuration data type to hold this variables so your application can access them. Normally you'd have a bunch of calls to lookupEnv in order to build your data type. This is tedious and error-prone. Thankfully, in Haskell we can do better!

import GHC.Generics
import System.Environment.FromEnv

data Config = Config
    { configDbUrl     :: !String
    , configApiSecret :: !String
    }
    deriving Generic

instance FromEnv Config

main = do
    config <- fromEnv
    -- do something with config

And that's it! By deriving Generic you can now create an instance of FromEnv for free. Check out the haddocks for more.

License

MIT