Safe Haskell | None |
---|---|
Language | Haskell98 |
System.Log.Logger.TH
Description
This module provides functions that generate hslogger functions using Template Haskell.
Notes:
- System.Log.Logger must be imported qualified, and the qualifier must
match the qualifier given to
deriveLoggers
and/orderiveNamedLoggers
. - Don't forget to enable Template Haskell preprocessing: specify the pragma
LANGUAGE TemplateHaskell
at the top of your source file orextensions: TemplateHaskell
in your cabal file.
Documentation
Arguments
:: String | Must match qualifier on import of System.Log.Logger. |
-> [Priority] | List of priorities for which to generate logging functions. |
-> Q [Dec] |
Generate hslogger functions for a list of priorities.
Example usage:
module Foo.Bar ( ... ) where import System.Log.Logger.TH (deriveLoggers) import qualified System.Log.Logger as HSL $(deriveLoggers "HSL" [HSL.DEBUG, HSL.INFO])
Used this way, deriveLoggers
would generate the following functions:
infoM :: MonadIO m => String -> m () infoM s = liftIO (HSL.infoM "Foo.Bar" s) debugM :: MonadIO m => String -> m () debugM s = liftIO (HSL.debugM "Foo.Bar" s)
The other hslogger priorities follow the same pattern.
In versions prior to 2.0.0, hslogger-template generated functions that prepended the module name to the log message. I no longer feel that this is correct behavior. Instead, please make use of hslogger's formatting functionality. Example:
import System.IO (stderr) import System.Log.Formatter (simpleLogFormatter) import System.Log.Logger (rootLoggerName) import System.Log.Handler (setFormatter) import System.Log.Handler.Simple (streamHandler) import System.Log.Logger.TH (deriveLoggers) import qualified System.Log.Logger as HSL $(deriveLoggers "HSL" [HSL.DEBUG, HSL.INFO]) handler <- streamHandler stderr HSL.DEBUG >>= \h -> return $ setFormatter h $ simpleLogFormatter "$time $loggername $prio $msg" HSL.updateGlobalLogger rootLoggerName (HSL.setLevel HSL.DEBUG . HSL.setHandlers [handler])
Arguments
:: String | Message prefix, e.g., "SomeProgram: ". |
-> String | Must match qualifier on import of System.Log.Logger. |
-> [Priority] | List of priorities for which to generate logging functions. |
-> Q [Dec] |
Like deriveLoggers
, but allows you to specify a message prefix to be
automatically prepended to every log message.