To make your core a little bit more reliable you should not catch the general error but a NeoJSONParseError. And you need to guard the dictionary access. There is no guarantee you get something back that inlcudes key success and message.

Norbert

Am 13.12.2017 um 09:54 schrieb Ben Coman <btc@openinworld.com>:

hi Sven,

> On 13 Dec 2017, at 07:59, Ben Coman <btc@openinworld.com> wrote:
>
>
> With...
>   Object subclass: #BittrexResponse
>       instanceVariableNames: 'success message result'
>       classVariableNames: ''
>       package: 'Bittrex'
>
>   Object subclass: #BittrexMarketSummary
>       instanceVariableNames: 'MarketName High Low Volume Last
>                 BaseVolume TimeStamp Bid Ask OpenBuyOrders
>                 OpenSellOrders PrevDay Created DisplayMarketName'
>       classVariableNames: ''
>       package: 'Bittrex'
>
> this code works great when the response holds good data...
>   ZnClient new
>       url: 'https://bittrex.com/api/v1.1/public/getmarketSummary?market=BTC-LTC';
>       enforceHttpSuccess: true;
>       accept: ZnMimeType applicationJson;
>       contentReader: [ :entity | |reader|
>               reader := (NeoJSONReader on: entity readStream).
>               reader for: BittrexResponse do: [:m|
>                       m mapInstVar: #success.
>                       m mapInstVar: #message.
>                       (m mapInstVar: #result) valueSchema: #ResultArray].
>               reader for: #ResultArray customDo: [ :mapping |
>                        mapping listOfElementSchema: BittrexMarketSummary ].
>               reader mapInstVarsFor: BittrexMarketSummary.
>       reader nextAs: BittrexResponse ];
>    get.
>
> i.e. a raw response looking like this....
> (ZnClient new
>       url: 'https://bittrex.com/api/v1.1/public/getmarketsummary?market=BTC-LTC';
>       get) inspect.
> ==> "'{""success"":true,""message"":"",""result"":[{""MarketName"":""BTC-LTC"",""High"":0.01982450,""Low"":0.01285257,""Volume"":1436429.81313360,""Last"":0.01842000,""BaseVolume"":24841.17217724,""TimeStamp"":""2017-12-13T05:56:25.937"",""Bid"":0.01840001,""Ask"":0.01842000,""OpenBuyOrders"":10140,""OpenSellOrders"":6306,""PrevDay"":0.01439800,""Created"":""2014-02-13T00:00:00""}]}'"
>
>
> But for bad response looking like this...
> (ZnClient new
>       url: 'https://bittrex.com/api/v1.1/public/getmarketsummary?market=INVALID';
>       get) inspect.
> ==> {"success":false,"message":"INVALID_MARKET","result":null}
>
> the JSON handling code fails deep in the call stack with an error
>      "NeoJSONParseError: [ expected"
> which is not so friendly for users of the Bittrex library.
>
> What are the different/recommended approaches with Zinc
> for catching JSON errors such that I can pass "message"
> as a higher level Error up the stack to the Bittrex user.
>
>  cheers -ben


On 13 December 2017 at 15:37, Sven Van Caekenberghe <sven@stfx.eu> wrote:
BTW, this is no about Zinc, but about NeoJSON.

This is what I meant with variability that is hard to capture with a simple static type schema.

I have no time to try myself right now, but a custom mapping for ivar result (as in a block) might be able to see the difference and act accordingly.

 
okay.  So I played around tracing this through the debugger and for anyone else
with a similar need later, I ended up with the following... 

response := (ZnClient new 
enforceHttpSuccess: true;
accept: ZnMimeType applicationJson;
contentReader: 
[ :entity | 
[ |reader|
reader := (NeoJSONReader on: entity readStream).
reader for: BittrexResponse do: 
[:m| 
m mapInstVar: #success.
m mapInstVar: #message.
(m mapInstVar: #result) valueSchema: BittrexTicker
].
reader mapInstVarsFor: BittrexTicker.
reader nextAs: BittrexResponse
] on: Error do: 
[ :err | |json| 
json := NeoJSONReader fromString: entity contents. 
(json at: 'success') 
ifFalse: [ self error: (json at: 'message') ]
ifTrue: [ self error: 'UKNOWN ERROR' ]
] 
]) get. 


for which I get a nice pre-debug window titled "Error: INVALID_MARKET"

cheers -ben