VB6 - JsonBag, Another JSON Parser/Generator

[dilettante]

With SOAP basically a dead duck and XML itself fading in importance, JSON is becoming more and more important as a serialization format today.

I've seen a number of VB6 JSON implementations around, including a couple posted right here in the CodeBank. Sadly none of them are very good, with little quirks and latent bugs (like improperly handling numeric data). Most of these ignore and flout the JSON standards at JSON too!

In any case I have my own implementation designed to conform as closely as possible to the standard, and now at version 1.6 it seems mature enough to share. I rewrote my notes into six pages of documentation which should make it a bit easier for others to use.


Bug reports are welcome. Though it seems to be working fine it is hard to prove code to be correct and there are probably edge cases I've never encountered.

Performance seems more than adequate for its purpose, which is mainly access to cloud computing services. Local config files are probably best still handled as plain old INI format files, though one could use JSON for that as well I suppose.


There is just one Class involved: JsonBag.cls, and as the documentation suggests it should be easy enough to import into a VBA host (Excel, etc.) as long as you tweak the API calls for 64-bit hosts when required.


The attachment includes this Class along with the documentation in RTF format, packaged up as a testbed Project JsonBagTest.vbp:

As you can see JsonBag supports a Whitespace property to format JSON for readability. By default compact JSON is generated.


Accessing the "document model" and creating JSON documents in code is easy enough. This is illustrated by a fragment from the test Project:

Private Sub cmdGenSerialize_Click()
    With JB
        .Clear
        .IsArray = False 'Actually the default after Clear.

        ![First] = 1
        ![Second] = Null
        With .AddNewArray("Third")
            .Item = "These"
            .Item = "Add"
            .Item = "One"
            .Item = "After"
            .Item = "The"
            .Item = "Next"
            .Item(1) = "*These*" 'Should overwrite 1st Item, without moving it.

            'Add a JSON "object" to this "array" (thus no name supplied):
            With .AddNewObject()
                .Item("A") = True
                !B = False
                !C = 3.14E+16
            End With
        End With
        With .AddNewObject("Fourth")
            .Item("Force Case") = 1 'Use quoted String form to force case of names.
            .Item("force Case") = 2
            .Item("force case") = 3

            'This syntax can be risky with case-sensitive JSON since the text is
            'treated like any other VB identifier, i.e. if such a symbol ("Force"
            'or "Case" here) is already defined in the language (VB) or in your
            'code the casing of that symbol will be enforced by the IDE:

            ![Force Case] = 666 'Should overwrite matching-case named item, which
                                'also moves it to the end.
            'Safer:
            .Item("Force Case") = 666
        End With
        'Can also use implied (default) property:
        JB("Fifth") = Null

        txtSerialized.Text = .JSON
    End With
End Sub

Newst version here.