[Gambas-user] gb.web.JSONCollection parse problem

[T Lee Davidson]

On 2/21/19 2:54 PM, jeff zacher wrote:
> Two valid JSON files will not parse properly with a call to
> 
> JSON.Decode(<json file contents>, True)
> 
> Consider this is valid JSON:
> [
>    {
>     "name" : "Value",
>     "another" : "Value"
>    }
> ]
> 
> The above will decode as a Variant[] and not a JSONCollection.
> 
> Consider this other valid JSON:
> 
> {
>    "name" : "value",
>    "another" : {
>          "nestedname" : "value"
>    }
> }
> 
> These will return as JSONCollections.
> 
> This is somewhat as expected, however there is no way to gracefully detect what type of object has been decoded. Using Try 
> blocks to determine by trial and error which of the above forms of a JSON are present cannot be good programming form. The 
> TypeOf(<json file contents>) function gives a gb.object type of object for both. This is very problematic when parsing large 
> files. What is the proper work around or how is this been properly used in these cases  (what am I missing about this?)
> 

The first JSON content is actually not a Collection. It is an array (or list) of collections with only one element. So, it 
decodes as a Variant.

You can test the type of the object using the "IS" operator which differentiates between both types, whereas TypeOf is lazy.

' Gambas module file

Public Sub Main()

   Dim sJson1 As String = "[{\"name\": \"Value\", \"another\": \"Value\"}]"
   Dim sJson2 As String = "{\"name\": \"value\", \"another\": {\"nestedname\": \"value\"}}"
   Dim JsonResult As Variant

   JsonResult = JSON.Decode(sJson1)
   If JsonResult Is Collection Then
     Print "Collection"
   Else
     Print "Array of Collections"
   Endif

   JsonResult = JSON.Decode(sJson2)
   If JsonResult Is Collection Then
     Print "Collection"
   Else
     Print "Array of Collections"
   Endif

End


This code yields:
Array of Collections
Collection


___
Lee