Developing Web Applications with Haskell and Yesod

Chapter 18. Blog: i18n, Authentication, Authorization, and Database

This is a simple blog app. It allows an admin to add blog posts via a rich-text editor (nicedit), allows logged-in users to comment, and has full i18n support. It is also a good example of using a Persistent database, leveraging Yesod's authorization system, and templates. While in general we recommend placing templates, Persistent entity definitions, and routing in separate files, we'll keep it all in one file here for convenience. The one exception you'll see below will be i18n messages. We'll start off with our language extensions. In scaffolded code, the language extensions are specified in the cabal file, so you won't need to put this in your individual Haskell files. > {-# LANGUAGE OverloadedStrings, TypeFamilies, QuasiQuotes, > TemplateHaskell, GADTs, FlexibleContexts, > MultiParamTypeClasses #-} Now our imports. > import Yesod > import Yesod.Auth > import Yesod.Form.Nic (YesodNic, nicHtmlField) > import Yesod.Auth.BrowserId (authBrowserId) > import Data.Text (Text) > import Network.HTTP.Conduit (Manager, newManager, def) > import Database.Persist.Sqlite > ( ConnectionPool, SqlPersist, runSqlPool, runMigration > , createSqlitePool > ) > import Data.Time (UTCTime, getCurrentTime) > import Control.Applicative ((<$>), (<*>), pure) First we'll set up our Persistent entities. We're going to create both our data types (via mkPersist) and a migration function, which will automatically create and update our SQL schema. ...