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NeoJSON extension - easier list handling with NeoJSONPropertyMapping

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Ben Coman

NeoJSON extension - easier list handling with NeoJSONPropertyMapping

hi Sven,

With NeoJSON I have found several times in handling lists that

I need to indirect through #for:customDo: like this......

reader

for: ExercismProblems

do: [ :mapping |

self halt.

(mapper mapInstVar: #problems) valueSchema: #ArrayOfProblems ].

reader

for: #ArrayOfProblems

customDo: [ :mapping |

mapper listOfElementSchema: ExercismProblem ].

when I'd really like to be simpler and more concise like this...

reader

for: ExercismProblems

do: [ :mapping |

(mapping mapInstVar: #problems) listOfType: Array withElementSchema: ExercismProblem ].

so I'm seeking your feedback on the following hack which facilitates that.

(and if I missed something that already makes it simpler)

----------------------------

Object subclass: #NeoJSONPropertyMapping

instanceVariableNames: 'propertyName valueSchema getter setter collectionClass' "Added collectionClass"

NeoJSONPropertyMapping >> listOfType: aCollectionClass withElementSchema: elementSchema

collectionClass := aCollectionClass.

valueSchema := elementSchema

NeoJSONPropertyMapping >> readObject: anObject from: jsonReader

| value |

value := collectionClass

ifNil: [jsonReader nextAs: valueSchema] "nil by default retains the original behaviour"

ifNotNil: [jsonReader nextList: collectionClass of: valueSchema ].

setter value: anObject value: value

NeoJSONReader >> nextList: nextListClass of: schema "copied from #nextAs"

"Secondary interface to parse JSON.

Return a list of objects, each element according to schema."

^ nextListClass streamContents: [ :stream |

self parseListDo: [

stream nextPut: (self nextAs: schema) ] ]

----------------------------

Sample data is shown at: https://github.com/bencoman/pharogui-exercism/blob/master/README.md

with the following code to access it.

Object subclass: #ExercismAPI

instanceVariableNames: 'client rawResponse jsonResponse success message result'

classVariableNames: 'ApiKey'

package: 'Exercism'

ExercismAPI class >> configureApiKey: key

ApiKey := key.

ExercismAPI >> track: trackIdString

self path: 'v2/exercises/' , trackIdString.

ExercismAPI >> fetchTrack: trackIdString

|znclient response|

ApiKey ifNil: [ self error: 'ApiKey not configured. See class-side ExcercismAPI' ].

znclient := ZnClient new

https;

enforceHttpSuccess: true;

accept: ZnMimeType applicationJson;

host: 'x.exercism.io' .

znclient path: 'v2/exercises/' , trackIdString.

znclient queryAt: 'key' put: ApiKey.

^ [ response := znclient get ]

on: ZnHttpUnsuccessful

do: [ :exception | Transcript crShow: exception ]

fetchJsonTrack: trackIdString

| reader |

reader := NeoJSONReader on: (self fetchTrack: trackIdString) readStream.

reader

for: ExercismProblems

do: [ :mapper |

(mapper mapInstVar: #problems) listOfType: Array andElementSchema: ExercismProblem ].

^ reader nextAs: ExercismProblems

In Playground...

ExercismAPI configureApiKey: 'ec60c50cb50d4ffaa97903d5ebb3d5ff'.

(ExercismAPI new fetchJsonTrack: 'go') inspect

I'll reset the apikey shortly. You can get a new one from http://exercism.io/account/key.

cheers -ben

Sven Van Caekenberghe-2

Re: NeoJSON extension - easier list handling with NeoJSONPropertyMapping

Hmm, Ben,

Did you see NeoJSONCustomMapping's mapping method category ?

There you can already find #listOfElementSchema: #listOfType: #listOfType:andElementSchema: as well as #mapWithValueSchema:

I am guessing they do what you want, no ? Or am I missing something as well ?

Sven

> On 16 Jun 2018, at 20:27, Ben Coman <[hidden email]> wrote:
>
> hi Sven,
>
> With NeoJSON I have found several times in handling lists that
> I need to indirect through #for:customDo: like this......
>
> reader
> for: ExercismProblems
> do: [ :mapping |
> self halt.
> (mapper mapInstVar: #problems) valueSchema: #ArrayOfProblems ].
> reader
> for: #ArrayOfProblems
> customDo: [ :mapping |
> mapper listOfElementSchema: ExercismProblem ].
>
>
> when I'd really like to be simpler and more concise like this...
>
> reader
> for: ExercismProblems
> do: [ :mapping |
> (mapping mapInstVar: #problems) listOfType: Array withElementSchema: ExercismProblem ].
>
> so I'm seeking your feedback on the following hack which facilitates that.
> (and if I missed something that already makes it simpler)
>
> ----------------------------
> Object subclass: #NeoJSONPropertyMapping
> instanceVariableNames: 'propertyName valueSchema getter setter collectionClass' "Added collectionClass"
>
>
> NeoJSONPropertyMapping >> listOfType: aCollectionClass withElementSchema: elementSchema
> collectionClass := aCollectionClass.
> valueSchema := elementSchema
>
>
> NeoJSONPropertyMapping >> readObject: anObject from: jsonReader
> | value |
> value := collectionClass
> ifNil: [jsonReader nextAs: valueSchema] "nil by default retains the original behaviour"
> ifNotNil: [jsonReader nextList: collectionClass of: valueSchema ].
> setter value: anObject value: value
>
>
> NeoJSONReader >> nextList: nextListClass of: schema "copied from #nextAs"
> "Secondary interface to parse JSON.
> Return a list of objects, each element according to schema."
>
> ^ nextListClass streamContents: [ :stream |
> self parseListDo: [
> stream nextPut: (self nextAs: schema) ] ]
> ----------------------------
>
> Sample data is shown at: https://github.com/bencoman/pharogui-exercism/blob/master/README.md
> with the following code to access it.
>
> Object subclass: #ExercismAPI
> instanceVariableNames: 'client rawResponse jsonResponse success message result'
> classVariableNames: 'ApiKey'
> package: 'Exercism'
>
>
> ExercismAPI class >> configureApiKey: key
> ApiKey := key.
>
>
> ExercismAPI >> track: trackIdString
> self path: 'v2/exercises/' , trackIdString.
>
>
> ExercismAPI >> fetchTrack: trackIdString
> |znclient response|
> ApiKey ifNil: [ self error: 'ApiKey not configured. See class-side ExcercismAPI' ].
> znclient := ZnClient new
> https;
> enforceHttpSuccess: true;
> accept: ZnMimeType applicationJson;
> host: 'x.exercism.io' .
> znclient path: 'v2/exercises/' , trackIdString.
> znclient queryAt: 'key' put: ApiKey.
> ^ [ response := znclient get ]
> on: ZnHttpUnsuccessful
> do: [ :exception | Transcript crShow: exception ]
>
>
> fetchJsonTrack: trackIdString
> | reader |
> reader := NeoJSONReader on: (self fetchTrack: trackIdString) readStream.
> reader
> for: ExercismProblems
> do: [ :mapper |
> (mapper mapInstVar: #problems) listOfType: Array andElementSchema: ExercismProblem ].
> ^ reader nextAs: ExercismProblems
>
>
> In Playground...
>
> ExercismAPI configureApiKey: 'ec60c50cb50d4ffaa97903d5ebb3d5ff'.
>
> (ExercismAPI new fetchJsonTrack: 'go') inspect
>
>
> I'll reset the apikey shortly. You can get a new one from http://exercism.io/account/key.
>
> cheers -ben

Ben Coman

Re: NeoJSON extension - easier list handling with NeoJSONPropertyMapping

On 17 June 2018 at 02:47, Sven Van Caekenberghe <[hidden email]> wrote:

Hmm, Ben,

Did you see NeoJSONCustomMapping's mapping method category ?

There you can already find #listOfElementSchema: #listOfType:

#listOfType:andElementSchema: as well as #mapWithValueSchema:

Yes. Indeed thats where I copied my selector naming from, although I switched "with" for ''and"

NeoJSONPropertyMapping >> listOfType:withElementSchema:

However NeoJSONCustomMappings seems only accessible through "reader for: ... customDo: "
while instance variable interaction seems only possible using "reader for: ... do:"

So it seems NeoJSONCustomMapping lacks #mapAccessor* methods

while NeoJSONObjectMapping lacks #listOfType:* methods

and "never the twain shall meet".

I didn't look closely at #mapWithValueSchema:

but its covering tests seem to operate on Dictionaries rather than Arrays.

I am guessing they do what you want, no ? Or am I missing something as well ?

Yes, but how to mix those list* methods with poking the result into an instance variable

to be able to "assign a list of elements to an instance variable" as a one liner?

I'd be glad to be shown another way to do this for the given data.

I see a few #testLists examples, but none that assign the result to an instance variable.

NeoJSONExamplesTests has some "lists of objects" tests, but no "objects with lists"

A useful example would be #testPolygonPoints...

NeoJSONExamplesTests >> testPolygonPoints

| polygon polygonJson result |

polygon := Polygon new vertices: { 1@2. 3@4. 5@6 }.

polygonJson :=

'{ "vertices": [ "I'm not clear on how to do the writer side of things"

{

"x" : 1,

"y" : 2

{

"x" : 3,

"y" : 4

{

"x" : 5,

"y" : 6

}]

}'.

result := (NeoJSONReader on: polygonJson readStream)

mapInstVarsFor: Point;

for: Polygon do: [ :mapping |

(mapping mapInstVar: #vertices) listOfType: Array withElementSchema: Point];

nextAs: Polygon.

self assert: result equals: polygon

Some equality support is needed for Polygon (PathShape)
(my best guess, discussion of this might be worth a separate thread)

PathShape >> = aPathShape

|otherVertices equal|

otherVertices := aPathShape vertices.

(self species = aPathShape species) & (vertices size = otherVertices size)

ifFalse: [ ^false ].

1 to: vertices size do: [ :i |

(vertices at: i) = (otherVertices at: i) ifFalse: [^false] ].

^true

PathShape >> hash

|hash|

hash := 0.

1 to: vertices size do: [ :i | hash bitXor: (vertices at: i) ].

^hash

cheers -ben

Sven

> On 16 Jun 2018, at 20:27, Ben Coman <[hidden email]> wrote:
>
> hi Sven,
>
> With NeoJSON I have found several times in handling lists that
> I need to indirect through #for:customDo: like this......
>
> reader
> for: ExercismProblems
> do: [ :mapping |
> self halt.
> (mapper mapInstVar: #problems) valueSchema: #ArrayOfProblems ].
> reader
> for: #ArrayOfProblems
> customDo: [ :mapping |
> mapper listOfElementSchema: ExercismProblem ].
>
>
> when I'd really like to be simpler and more concise like this...
>
> reader
> for: ExercismProblems
> do: [ :mapping |
> (mapping mapInstVar: #problems) listOfType: Array withElementSchema: ExercismProblem ].
>
> so I'm seeking your feedback on the following hack which facilitates that.
> (and if I missed something that already makes it simpler)
>

cheers -ben