Web.RBB.Blog.Query

This module provides some functions and data types that can be used to manage search and query data for a list of Entry values.

Documentation

data EntryQuery

The request data provided inside a URL.

Example: ?id=42&sortBy=Identifier

Example backend implementation using the Happstack package:

 import Happstack.Server (look, HasRqData, ServerPartT)

 maybeLookAndRead :: (Monad m, Read a, Alternative m, HasRqData m)
                  => a -> String -> m a
 maybeLookAndRead a qry = do
     l <- optional $ look qry
     return $ fromMaybe a (maybe (Just a) readMaybe l)

 -- | Parse the supported request data and present it in a data type.
 parseQueryRqData :: ServerPartT IO EntryQuery
 parseQueryRqData = EntryQuery
     <$> (sortMethodToComparator
         <$> maybeLookAndRead Update "sortBy"
         <*> maybeLookAndRead Descending "sortOrder")

Constructors

EntryQuery

Fields

eqSortBy :: Entry -> Entry -> Ordering

The method entries are sorted by.

Instances

Default EntryQuery

The Default instance for an EntryQuery type contains a function that sorts the entries descending by the last update to the entry.

Sorting

data SortMethod

Simple enum that provides Show and read instances so that a parser can convert the sting directly to a value of this type.

Constructors

Update

Identifier

Author

Instances

Enum SortMethod

Eq SortMethod

Ord SortMethod

Read SortMethod

Show SortMethod

data SortOrder

Constructors

Ascending

Descending

Instances

Enum SortOrder

Eq SortOrder

Ord SortOrder

Read SortOrder

Show SortOrder

sortMethodToComparator :: SortMethod -> SortOrder -> Entry -> Entry -> Ordering

Convert a SortMethod value to a sorting function that can be used in confunction with functions sortBy from Data.List.