Stability	experimental
Maintainer	woozletoff@gmail.com
Safe Haskell	None

Web.RBB.Blog.Query

Contents

Sorting

Description

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

Synopsis

Documentation

data EntryQuery Source

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 Source

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 Source

Constructors

Ascending
Descending

Instances

Enum SortOrder
Eq SortOrder
Ord SortOrder
Read SortOrder
Show SortOrder

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

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