[Development] json api for modifying document

lars.knoll at nokia.com lars.knoll at nokia.com
Thu May 10 09:21:07 CEST 2012

On 5/10/12 5:59 AM, "ext Girish Ramakrishnan" <girish at forwardbias.in>

>Hi Lars,
>The current API appears to make modifications to values instead of the
>document itself. This makes it quite cumbersome to modify a document.
>For example, to change the value of 5 to 10 in the json "[1, 2, [3, 4,
>[5, 6]]]", one has to write the following code.
>    QJsonDocument doc = QJsonDocument::fromJson("[1, 2, [3, 4, [5, 6]]]");
>    QJsonArray a1 = doc.array();
>    QJsonArray a2 = a1[2].toArray();
>    QJsonArray a3 = a2[2].toArray();
>    a3[0] = 10;
>    a2[2] = a3;
>    a1[2] = a2;
>AFAICT, to change a value somewhere in the document, one has to update
>and then update all the way up.

Yes, the API is following implicit sharing paradigms as we have it most
other places in Qt. The problem with modifying the document directly is
that it'll be rather inefficient if you have to modify several values in
the inner array.

>So, if I didn't miss something, may I suggest that we make this like
>the QWebElement API (which makes modifications to the DOM tree

This is a very large behavioral change and IMO comes too late now. The
jsondb module e.g. relies heavily on the QJson classes and such a change
would silently break a lot of code there.

One option I see is to add some API for 5.1 that returns references
instead of values. We already have QJsonValueRef, maybe that scheme can be
extended to also allow for references to arrays and objects.


More information about the Development mailing list