cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
Showing results for 
Search instead for 
Did you mean: 

Bug ? JSON array returns {} from data table

Pearl

Bug ? JSON array returns {} from data table

Hi, 

I have a data table and one of the fields is JSON type .   I can write a JSON object into the table successfully,  but when getting the JSON object back,  the array property of the JSON object becomes {}. 

 

The workaround is that I have to convert the array field into String and then call JSON.parse to get the JSON array back . 

Is it a known issue ?  

 

I uploaded a reproducible XML file for the problem , you can run AddJsonValue firstly , then run  GetJson to observe the log  . 

 

ThingWorx 8.4.2 + PostgreSQL 10

 

Regards,

Sean

 

7 REPLIES 7

Re: Bug ? JSON array returns {} from data table

Hello Sean,

 

The DataTables work fine, the actual issue is with JSON.stringify, which doesn't traverse complete JSON object. E.g. this code outputs "1" as expected:

logger.debug("The original json array fileDataBatchLines:" + JSON.stringify(fileDataBatchLines[0][0]));

 

We created a trivial (four lines of code) ThingWorx extension to work around this issue, here it is: https://github.com/vilia-fr/twxdevext

 

You can use it as following:

var str = Resources["DevelopFunctions"].JsonToString({ json: fileDataBatchLines });
logger.debug("The original json array fileDataBatchLines:" + str);

In the log you can see complete JSON, with "_" standing for line breaks to improve readability.

 

DISCLAIMER: We don't support this extension officially, use it on your own risk. I bet there's a better, more standard way to do it, I just don't know about it.

 

/ Constantine

Re: Bug ? JSON array returns {} from data table

Sorry Sean,

 

Forget about extension -- I checked, and we've made it only to put linebreaks inside the output. Just skip JSON.stringify altogether and it'll work:

logger.debug("The original json array fileDataBatchLines:" + fileDataBatchLines);

 

/ Constantine

Re: Bug ? JSON array returns {} from data table

@Constantine ,

But if I use the original  fileDataBatchLines directly,  it doesn't has the array functions, such as : concat, filter.   

 

Regards,

Sean

 

Re: Bug ? JSON array returns {} from data table

Sean,

ThingWorx wraps arrays into json objects with property « array ». Try fileDataBatchLines.array.filter.

/ Constantine

Re: Bug ? JSON array returns {} from data table

@Constantine ,

 

I tried the statement below,  but got error because fileDataBatchLines.array is undefined .  

 

logger.debug("fileDataBatchLines.array:" + fileDataBatchLines.array);
fileDataBatchLines.array.filter(function(item){
    logger.debug("item: " + item);
});

Re: Bug ? JSON array returns {} from data table

Hello Sean,

 

Sorry for the late reply.

 

AFAIK JavaScript array filter() method was introduced in ECMAScript 5, while ThingWorx supports JavaScript 1.7, which corresponds to ECMAScript 3 with some extensions. Under the hood ThingWorx uses Rhino 1.7r4 as its JavaScript engine. Although support for ECMAScript 5 was introduced in 1.7r3, it is not used by default, so ThingWorx sticks to JavaScript 1.7, which is described in Help and a couple of Tech Support tickets.

 

Regards,
Constantine

Re: Bug ? JSON array returns {} from data table

@Constantine ,

Thank you for the explanation .  

 

If call javaScript array concat() , it also raise function undefined error.  But concat() was introduced in Javascript 1.2. 

 

In a summary: 

  • fileDataBatchLines.concat  //undefined
  • fileDataBatchLines.array    //undefined