There are several 3rd party JSON libraries that play nicely with Qt. Could using one of those be an option?

I assume you mean Javascript libraries. Is there one you know works ok with Qt?

Thanks

Simon

Actually I was referring to C++ libraries:-)

I assume there is (or will be) a better way to do all with javascript but if not you can’t find out or wait you can always use the script module on c++ to parse the json output and expose the result to qml as a model.

I am not convinced “all Javascript” is a better way! Javascript is much slower than C++ and with a animation running at 60 frames per second you do not have all that much time to update your state…

I agree that is will not be the most efficient way but one of the goals for QML must be to make easier for the web developers to start writing qml code.

In theory all that we need is to make a http request that will give us a string and an “evaluateJavascript” function :)

Kidding apart, I would just try to create a qml extension in c++ that would return a “generic” model for any URI. I can only imagine that soon or later “qt” will have to provide a standard implementation for this.

I’m agreed with Tobias. I think that I will prefer QAbstractItemModel that will parse JSON (with one of libraries Tobias told about) and use it as model for QML ListView instead of doing all work in JS.

Parsing JSON is easy and no additional libraries are required, you can just use eval(), JSON structure is a valid javascript code, right?

Cezary Tomczak, yes, but you need to build model from object you will receive after eval, it will take processor time, not JSON parsing.

Having done some more research, Cezary is correct. While it would be nice to have a JSONListModel, something similar can be achieved using the sample shown at http://bugreports.qt.nokia.com/browse/QTBUG-12117

After other comments it would be useful to know the performance implications of doing this vs doing it in Qt c++

Simon Judge

SimonJudge, all depends on your JSON size. If it is not big, than JS way is ok for you. But if it contains a lot of elements, then using c++ will be better.

Hey a good Qt/C++ JSON parser is avaliable with a LGPL licence: http://qjson.sourceforge.net/
Might be what you need.

luizpaulo wrote:

Hey a good Qt/C++ JSON parser is avaliable with a LGPL licence: http://qjson.sourceforge.net/ Might be what you need.

I saw it when I was working on a simple json parser but decided against it. Depending on the task you can get the same result w/o any additional dependencies – just using the script module.

Hello here is my point of view! I tested everything! XMLModel, javascript XML parser, C++ side parser etc…

1. Do Not use C++ Json parser : Because exchange data between c++ and QML is slow
2. Make a Javascript parser ! It’s more easy with eval ! Here is an example :

Json data

QML side : main.qml

javascript side : parser.js

It is a little surprising to me that you found that exchanging data between C++ and QML to be slow.

I can imagine that maybe the C++ xml parser you tried is slow but I can’t imagine creating the model in c++ can be any slower than creating it using Javascript.

Another scenario I can imagine it would slow things is if you are adding elements to a model that is already in use.

I am just curious of the why…