On 5 December 2017 at 20:44, Sven Van Caekenberghe <sven@stfx.eu> wrote:

> On 5 Dec 2017, at 13:33, Ben Coman <btc@openinworld.com> wrote:

> @sven, I started reading Enterprise Pharo a couple of hours ago.
> I don't quite get your section references. I presume you
> don't mean "chapter 11 Persisting Objects with Voyage, 11.3 Enhancing Storage"
> That seems off topic. And "chapter 4�� Zinc HTTP: The Client Side, 4.11 Headers"
> doesn't have a sub-part "3".

I meant 11.3 in this page https://ci.inria.fr/pharo-contribution/job/EnterprisePharoBook/lastSuccessfulBuild/artifact/book-result/Zinc-HTTP-Server/Zinc-HTTP-Server.html a section called 11.3. A Zinc Client.

> I guess part of what I'm interested in are patterns for hooking
> NeoJSON up to parse a REST response into objects to build a wrapper
> around a REST service. I see a chapter in Enterprise Pharo, which I'll
> get to that soon.�� Perhaps I was premature asking before reading that,
> but its good to have a few paths to explore.

Here is a recent example http://forum.world.st/Another-example-of-invoking-a-REST-JSON-web-service-resolving-User-Agent-strings-tt5017489.html

Thanks Sven.�� That helped a lot.�� I'd like to report success.

It may be useful to others to see how to progressively build up to parsing a Nested JSON REST

1. First parse the JSON into simple Dictionaries...

(ZnClient new��

url: 'https://bittrex.com/api/v1.1/public/getmarkets';

enforceHttpSuccess: true;

accept: ZnMimeType applicationJson;

contentReader: [ :entity | NeoJSONReader fromString: entity contents ];

get) inspect.

==>Dictionary(��

�� 'success' ==> true

�� 'message' ==> ''

�� 'result ' ==> an Array(a Dictionary('BaseCurrency'->'BTC' 'BaseCurrencyLong'->'Bitcoin')��

... a Dictionary('BaseCurrency'->'ETH' 'BaseCurrencyLong'->'Ethereum')��

2. Then parse the first level response into a real object...

Object subclass: #BittrexResponse

instanceVariableNames: 'success message result'

classVariableNames: ''

package: 'Bittrex'

(ZnClient new��

url: 'https://bittrex.com/api/v1.1/public/getmarkets';

enforceHttpSuccess: true;

accept: ZnMimeType applicationJson;

contentReader: [ :entity |��

(NeoJSONReader on: entity readStream)

mapInstVarsFor: BittrexResponse ;

�� nextAs: BittrexResponse ];

�� get) inspect.

==>BittrexResponse

�� success => true

�� message => ''��

�� result => an Array(a Dictionary('BaseCurrency'->'BTC' 'BaseCurrencyLong'->'Bitcoin')��

... a Dictionary('BaseCurrency'->'ETH' 'BaseCurrencyLong'->'Ethereum')��

Or alternatively...

(ZnClient new��

url: 'https://bittrex.com/api/v1.1/public/getmarkets';

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 ].

�� reader nextAs: BittrexResponse ];

�� get) inspect.

==>BittrexResponse

�� success => true

�� message => ''��

�� result => an Array(a Dictionary('BaseCurrency'->'BTC' 'BaseCurrencyLong'->'Bitcoin')��

... a Dictionary('BaseCurrency'->'ETH' 'BaseCurrencyLong'->'Ethereum')��

3. Finally parse into real objects��the nested level holding the data you really want...

Object subclass: #Market

instanceVariableNames: 'MarketCurrency BaseCurrency MarketCurrencyLong BaseCurrencyLong MinTradeSize MarketName IsActive Created Notice IsSponsored LogoUrl'

classVariableNames: ''

package: 'Bittrex'

(ZnClient new��

url: 'https://bittrex.com/api/v1.1/public/getmarkets';

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: #ArrayOfMarkets].

reader for: #ArrayOfMarkets customDo: [ :mapping | mapping listOfElementSchema: Market ].

reader mapInstVarsFor: Market.��

�� reader nextAs: BittrexResponse ];

�� get) inspect.

==>BittrexResponse

�� success => true

�� message => ''��

�� result => an Array(a Market(LTC) a Market(DOGE) a Market(VTC) a Market(PPC) a Market(FTC) a Market(RDD)��

... Market(POWR) a Market(BTG) a Market(BTG) a Market(BTG) a Market(ADA) a Market(ENG) a Market(ENG))

WhooHoo!

A couple of things remaining:

* The instance variables of Market currently start with an upper-case to match the JSON fields.

�� Lower-casing the first letter breaks things.��

�� What strategies can be used to conform here to Smalltalk conventions?

�� Or is it easy enough to live with it?

* In various posts I've seen mention of a class-side method #neoJsonMapping:

�� but there is no explanation of this in��the Enterprise Book.��

�� How might #neoJsonMapping:��come into the picture for my use case above?

cheers -ben