[Haskell-cafe] api-tools questions

[Karsten Gebbert]

Hi,

I managed to my example working by using a record type to convert
from/to (similar to the examples in your library Chris). Yay! I am still
not sure why it didn't work when I used newtype/type to serialize
to/from.

Thanks for your help anyways :)

k


Karsten Gebbert <k at ioctl.it> writes:

> Hi Adam,
>
> somehow I can't get it to work according to yours and Chris' examples. I
> have the following test-case:
>
>   -----
>
>   stamp :: TimeStamp
>     = basic string 
>       with inj_TimeStamp, prj_TimeStamp
>   
>   test :: TestRec
>     = record 
>       created_at :: TimeStamp
>
>   -----
>
>   $(generate tests)
>   
>   -- created_at parses with:
>   -- parseTime defaultTimeLocale "%Y-%m-%d %H:%M:%S%Q" a
>   
>   type TimeStamp = Maybe UTCTime
>
>   inj_TimeStamp :: REP__TimeStamp -> ParserWithErrs TimeStamp
>   inj_TimeStamp  (REP__TimeStamp as) = 
>     return $ parseTime defaultTimeLocale "%Y-%m-%d %H:%M:%S%Q" (Text.unpack as)
>   
>   prj_TimeStamp :: TimeStamp -> REP__TimeStamp
>   prj_TimeStamp (Just mp) = REP__TimeStamp $ 
>     Text.pack $ formatTime defaultTimeLocale "%Y-%m-%d %H:%M:%S%Q" mp
>   prj_TimeStamp  Nothing   = REP__TimeStamp $ 
>     Text.pack ""
>   
>   $(generateAPITools tests [enumTool, jsonTool])
>
>
> But, when I use it like this, I still get the format error:
>
>    λ import qualified   Data.ByteString.Lazy as LBS                                       
>    λ import Mytest.Types                                                        
>    λ let a =  "{ \"created_at\": \"2014-09-10 14:06:48.13972\" }" :: LBS.ByteString       
>    λ decodeWithErrs a :: Either [(JSONError, Position)] TestRec                           
>    Left [(BadFormat FmtUTC "UTC" "2014-09-10 14:06:48.13972",[InField "created_at"])]      
>
> It seems its not using the functions provided to parse the result at
> all, if I put in some bogus stuff the conversion functions and set the
> type of TimeStamp to Text, the created_at string appears in the output:
>
>   inj_TimeStamp :: REP__TimeStamp -> ParserWithErrs TimeStamp
>   inj_TimeStamp  (REP__TimeStamp _) = 
>     return $ Text.pack "heheheheh"
>   
>   prj_TimeStamp :: TimeStamp -> REP__TimeStamp
>   prj_TimeStamp _ = REP__TimeStamp $ Text.pack "Hohoho"
>
>   λ let a =  "{ \"created_at\": \"2014-09-10 14:06:48.13972\" }" :: LBS.ByteString        
>   λ decodeWithErrs a :: Either [(JSONError, Position)] TextRec                            
>   Right (TextRec {_test_created_at = "2014-09-10 14:06:48.13972"})                         
>
> I'm probably missing something really simple here, but maybe you can
> spot it quicker than I do.. I'll investigate more when I'm back home
> anyways.
>
> Thanks for any hints!
>
> k
>
> Adam Gundry <adam at well-typed.com> writes:
>
>> Hi Karsten,
>>
>> This isn't very well documented, but there is a (hidden) feature of
>> api-tools that should do what you want. If you say something like
>>
>>     mt :: MyTime = basic string with inj_MyTime, prj_MyTime
>>
>> then you can define your own type MyTime and give conversion functions
>> inj_MyTime and prj_MyTime to convert back and forth from a
>> newtype-wrapped Text. (In fact, you could probably use UTCTime as
>> MyTime...). More precisely, api-tools will generate something like
>>
>>     newtype REP__MyTime = REP__MyTime Text
>>
>> and you will need to implement
>>
>>     inj_MyTime :: REP__MyTime -> ParserWithErrs MyTime
>>     prj_MyTime :: MyTime -> REP__MyTime
>>
>> I hope this helps, and further questions or documentation contributions
>> are very welcome!
>>
>> Cheers,
>>
>> Adam
>>
>>
>> On 09/09/14 14:02, Karsten Gebbert wrote:
>>> Hi All,
>>> 
>>> I have a question concerning the api-tools package.
>>> 
>>> Its not clear from the tests, sources or the tutorial how I can use
>>> other date/time formats that the default `utc` type can handle. I'm
>>> trying to wrap a JSON API that is not under my control, so I have to
>>> adhere to whatever I get back from it. Could anybody with experience
>>> with the package point me to some example, relevant bits in the sources
>>> or a tip how to do it?
>>> 
>>> I'm planning to create some more documentation around the package to
>>> contribute back once I figured out a few more details, because I think
>>> its quite a useful abstraction when dealing with (foreign) APIs IMO.
>>> 
>>> Thanks already for any hints,
>>> 
>>> karsten
>>
>>
>> -- 
>> Adam Gundry, Haskell Consultant
>> Well-Typed LLP, http://www.well-typed.com/
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