| Portability | portable |
|---|---|
| Stability | experimental |
| Maintainer | Joel Lehtonen <joel.lehtonen+curlaeson@iki.fi> |
| Safe Haskell | None |
Network.Curl.Aeson
Description
Functions for communicating with JSON over HTTP connection.
- curlAesonGet :: FromJSON a => URLString -> IO a
- curlAesonGetWith :: (Value -> Parser a) -> URLString -> IO a
- curlAeson :: ToJSON a => (Value -> Parser b) -> String -> URLString -> [CurlOption] -> Maybe a -> IO b
- cookie :: String -> String -> CurlOption
- rawJson :: String -> Maybe Value
- (...) :: FromJSON b => Parser Object -> Text -> Parser b
- noData :: Maybe Value
- data CurlAesonException = CurlAesonException {}
How to use this library
To get bid and ask levels as a pair from a Bitcoin exchange using its public API:
{-# LANGUAGE OverloadedStrings #-}
import Control.Monad
import Data.Aeson
import Network.Curl.Aeson
ticker :: IO (Double,Double)
ticker = curlAesonGetWith p "https://bitcoin-central.net/api/v1/ticker/eur"
where
p (Object o) = do
bid <- o .: "bid"
ask <- o .: "ask"
return (bid,ask)
p _ = mzero
The same as above, but we define our own data type which is an instance of FromJSON:
{-# LANGUAGE OverloadedStrings #-}
import Control.Applicative
import Control.Monad
import Data.Aeson
import Network.Curl.Aeson
data Ticker = Ticker { bid :: Double
, ask :: Double
} deriving (Show)
instance FromJSON Ticker where
parseJSON (Object o) = Ticker <$> o .: "bid" <*> o .: "ask"
parseJSON _ = mzero
ticker :: IO Ticker
ticker = curlAesonGet "https://bitcoin-central.net/api/v1/ticker/eur"
Sending HTTP request
curlAesonGet :: FromJSON a => URLString -> IO aSource
Shorthand for doing just a HTTP GET request and parsing the output to any FromJSON instance.
curlAesonGetWith :: (Value -> Parser a) -> URLString -> IO aSource
Shorthand for doing just a HTTP GET request and parsing the output with given parser p.
Arguments
| :: ToJSON a | |
| => (Value -> Parser b) | Parser for response. Use |
| -> String | Request method |
| -> URLString | Request URL |
| -> [CurlOption] | Session cookies, or other cURL options. Use empty list if you don't need any. |
| -> Maybe a | JSON data to send, or Nothing when sending request without any content. |
| -> IO b | Received JSON data |
Send single HTTP request.
The request automatically has Content-type: application/json
header if you pass any data. This function is lenient on response
content type: everything is accepted as long as it is parseable
with decode. HTTP payload is expected to be UTF-8 encoded.
If you need authentication, you need to pass session cookie or
other means of authentication tokens via CurlOption list.
Helper functions
cookie :: String -> String -> CurlOptionSource
Single cookie of given key and value.
rawJson :: String -> Maybe ValueSource
Useful for just giving the JSON as string when it is static anyway and doesn't need to be programmatically crafted.
Arguments
| :: FromJSON b | |
| => Parser Object | Parser to JSON object to look into |
| -> Text | Key to look for |
| -> Parser b | Parser to the resulting field |
Helper function for writing parsers for JSON objects which are not needed to be parsed completely.
In this example we are parsing JSON from
http://json.org/example.html. Note the use of the
OverloadedStrings language extension which enables Text values
to be written as string literals.
p (Objecto) =pureobj..."glossary"..."title" p _ =mzero
To avoid ambiguity in type checker you may pass this value instead
of Nothing to curlAeson.
Exception handling
data CurlAesonException Source
This exception is is thrown when Curl doesn't finish cleanly or the parsing of JSON response fails.
Constructors
| CurlAesonException | |