Data.Yaml.Config

Library for read config files in YAML format.

example.yaml:

 server:
     port: 8080
     logs:
         access: /var/log/server/access.log
         error:  /var/log/server/error.log

Usage example:

 module Main where
 import Prelude hiding (lookup)
 import Data.Word (Word16)
 import Data.Yaml.Config (load, subconfig, lookupDefault, lookup)

 main :: IO ()
 main = do
     config <- load "./example.yaml"

     serverConfig <- subconfig "server" config
     let interface = lookupDefault "interface" "127.0.0.1" serverConfig
         port :: Word16 = lookupDefault "port" 80 serverConfig

     logConfig <- subconfig "logs" serverConfig
     accessLog <- lookup "access" logConfig
     errorLog <- lookup "error" logConfig

     mapM_ putStrLn [interface, (show port), errorLog, accessLog]

Documentation

data Config

Type contains config section and path from root.

Instances

Eq Config

Show Config

NFData Config

type Key = Text

Config or field name

newtype KeyError

This error can be raised if config has not target path.

Constructors

KeyError Key

Instances

Show KeyError

Typeable KeyError

Exception KeyError

load :: FilePath -> IO Config

Find file in filesystem and try to load it as YAML config. May fail with InvalidYaml if file not found.

>>> config <- load "example.yaml"

keys :: Config -> [Key]

Show all first level config field's.

>>> keys config
["section1","section2"]

subconfig

Arguments

:: Failure KeyError m

=> Key

Subconfig name

-> Config

(Sub)Config for find

-> m Config

Founded Subconfig

Get subconfig by name. May fail with KeyError if target key doesn't exist at current level.

>>> :set -XOverloadedStrings
>>> sub <- subconfig "section1" config

lookup

Arguments

:: (Failure KeyError m, FromJSON a)

=> Key

Field name

-> Config

Config for find

-> m a

Field value

Get value for given key. May fail with KeyError if key doesn't exist.

>>> keys sub
["field1","field2"]
>>> putStrLn =<< lookup "field1" sub
value1

lookupDefault

Arguments

:: FromJSON a

=> Key

Field name

-> a

Default value

-> Config

Config for find

-> a

Founded or default value

Find value in config and return it or return default value.

>>> lookupDefault "field3" "def" sub
"def"