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Need help with NeoJSON reader definition

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jtuchel

Need help with NeoJSON reader definition

Hi there,

I am having a hard time configuring a NeoJSONReader for a JSON file like
this:

{
     "Paging": { someStuff
        },
     "ErrorMessage": null,
     "ErrorCode": 0,
     "Data": [
         {object1},

         {object2}

         ]

}

Where I want to ignore everything but the list named "Data". (Of course
I'll have to take a look at ErrorMessages later, but one step after the
other...).

I've tried several combinations of mappers and always end up with
NoeJSON parsing Exceptions. I semm unable to see the obvious.

In The end I just want to only use the contents of the Data list and map
each entry in there to some smalltalk object. I was successful with
other structures and lists, but this time I am unable to see the forest
among all those trees.

Any hints?

Joachim

jtuchel

Re: Need help with NeoJSON reader definition

I probably need to send a bit more info.

My latest attempt was this:

     mapper := NeoJSONReader new.

     mapper for: #RootObject customDo: [:mapping | mapping mapWithValueSchema: #TransferMessage].

     mapper

         for: #TransferMessage

         do: [:mapping |

             (mapping mapInstVar: 'Data' to: 'Data') listOfElementSchema: SomeExistingSmalltalkClass].

which results in

Symbol does not understand allInstVarNames

Please note there is no class named #TransferMessage in my Image. This
works for things like #ArrayOfPoints in the examples on the NeoJSON git
page and it also works in some of my other JSON mappings in different
contexts.

I guess this is because I cannot map to instvars if there is no
class/object to store values into...
So do I really need to implement an otherwise useless Smalltalk class
just to have something to map the outermost {} object to?

I also tried variations of for:customDo: for the mapping of the
#TransferMessage and had no success so far.

Any ideas?

Joachim

Am 26.09.17 um 08:29 schrieb [hidden email]:

> Hi there,
>
>
> I am having a hard time configuring a NeoJSONReader for a JSON file
> like this:
>
> {
>     "Paging": { someStuff
>        },
>     "ErrorMessage": null,
>     "ErrorCode": 0,
>     "Data": [
>         {object1},
>
>         {object2}
>
>         ]
>
> }
>
>
> Where I want to ignore everything but the list named "Data". (Of
> course I'll have to take a look at ErrorMessages later, but one step
> after the other...).
>
> I've tried several combinations of mappers and always end up with
> NoeJSON parsing Exceptions. I semm unable to see the obvious.
>
> In The end I just want to only use the contents of the Data list and
> map each entry in there to some smalltalk object. I was successful
> with other structures and lists, but this time I am unable to see the
> forest among all those trees.
>
> Any hints?
>
>
> Joachim
>
>
>
>
>

--
-----------------------------------------------------------------------
Objektfabrik Joachim Tuchel mailto:[hidden email]
Fliederweg 1 http://www.objektfabrik.de
D-71640 Ludwigsburg http://joachimtuchel.wordpress.com
Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1

Sven Van Caekenberghe-2

Re: Need help with NeoJSON reader definition

Hi Joachim,

Have a look at this new example:

===
Name: Neo-JSON-Tests-SvenVanCaekenberghe.43
Author: SvenVanCaekenberghe
Time: 26 September 2017, 2:14:01.71055 pm
UUID: f40af758-7816-0d00-89cd-641e08d6220e
Ancestors: Neo-JSON-Tests-SvenVanCaekenberghe.42

Add #testVirtualTransferObject as another mapping example
===

NeoJSONMappingTests>>#testVirtualTransferObject
| data customMapping extraJson json result |
data := NeoJSONObject new data: { 1@1. 2@2 }.
extraJson := '{"foo":1,"data":[{"x":1,"y":1},{"x":2,"y":2,"z":-1}]}'.
"The idea here is that we are not interested in the top level object just in its data property,
which should be of a specific type, hence we create a virtual transfer object"
customMapping := [ :mapper |
mapper
for: Point do: [ :mapping |
mapping mapInstVars: #(x y) ];
for: #ArrayOfPoints customDo: [ :mapping |
mapping listOfElementSchema: Point ];
for: #TransferObject do: [ :mapping |
mapping subjectClass: NeoJSONObject.
(mapping mapAccessor: #data) valueSchema: #ArrayOfPoints ];
yourself ].
"By using NeoJSONObject accessors (#data & #data:) are translated to generic #at:[put:] messages.
A longer alternative is
(mapping mapProperty: #data getter: [ :obj | obj at: #data ] setter: [ :obj :x | obj at: #data put: x]) valueSchema: #ArrayOfPoints
where the blocks give you the flexibility to use a plain Dictionary for example"
result := (customMapping value: (NeoJSONReader on: extraJson readStream)) nextAs: #TransferObject.
self assert: result equals: data.
json := String streamContents: [ :out |
(customMapping value: (NeoJSONWriter on: out)) nextPut: data as: #TransferObject ].
result := (customMapping value: (NeoJSONReader on: json readStream)) nextAs: #TransferObject.
self assert: result equals: data

Does this help ?

Sven

> On 26 Sep 2017, at 12:01, [hidden email] wrote:
>
> I probably need to send a bit more info.
>
> My latest attempt was this:
>
> mapper := NeoJSONReader new.
>
> mapper for: #RootObject customDo: [:mapping | mapping mapWithValueSchema: #TransferMessage].
>
> mapper
>
> for: #TransferMessage
>
> do: [:mapping |
>
> (mapping mapInstVar: 'Data' to: 'Data') listOfElementSchema: SomeExistingSmalltalkClass].
>
>
> which results in
>
> Symbol does not understand allInstVarNames
>
> Please note there is no class named #TransferMessage in my Image. This works for things like #ArrayOfPoints in the examples on the NeoJSON git page and it also works in some of my other JSON mappings in different contexts.
>
> I guess this is because I cannot map to instvars if there is no class/object to store values into...
> So do I really need to implement an otherwise useless Smalltalk class just to have something to map the outermost {} object to?
>
> I also tried variations of for:customDo: for the mapping of the #TransferMessage and had no success so far.
>
> Any ideas?
>
>
> Joachim
>
>
> Am 26.09.17 um 08:29 schrieb [hidden email]:
>> Hi there,
>>
>>
>> I am having a hard time configuring a NeoJSONReader for a JSON file like this:
>>
>> {
>> "Paging": { someStuff
>> },
>> "ErrorMessage": null,
>> "ErrorCode": 0,
>> "Data": [
>> {object1},
>>
>> {object2}
>>
>> ]
>>
>> }
>>
>>
>> Where I want to ignore everything but the list named "Data". (Of course I'll have to take a look at ErrorMessages later, but one step after the other...).
>>
>> I've tried several combinations of mappers and always end up with NoeJSON parsing Exceptions. I semm unable to see the obvious.
>>
>> In The end I just want to only use the contents of the Data list and map each entry in there to some smalltalk object. I was successful with other structures and lists, but this time I am unable to see the forest among all those trees.
>>
>> Any hints?
>>
>>
>> Joachim
>>
>>
>>
>>
>>
>
> --
> -----------------------------------------------------------------------
> Objektfabrik Joachim Tuchel mailto:[hidden email]
> Fliederweg 1 http://www.objektfabrik.de
> D-71640 Ludwigsburg http://joachimtuchel.wordpress.com
> Telefon: +49 7141 56 10 86 0 Fax: +49 7141 56 10 86 1
>
>