Django : provide dynamically generated data as attachment on button press

Question

Problem Overview:

I am creating a Django-based client with the intent of returning data from a web service. The goal of this project is to return data to the user from the web service based on the values selected by the user in a form. Upon the form submit, a query string is generated, sent to the web service and the page data is returned as a string. Currently, that data is displayed to the user in the browser. I want to provide the functionality that would allow the user to click a button and download the data.

Question:

How could I return the data to the user when they click a button in their browser for download? How do I make different options of the same data available (i.e. application/json, or text/csv)?

Current (not-working) Implementation:

I am attempting, and failing, to do the following:

views.py

Returning a render_to_response object of my template. To the template I pass the form, and the data in it's various forms.

def view(request):
    #Do stuff, get data as string

    #Get data into needed formats (see utils.py)
    jsonData  = jsonToJsonFile(dataString, fileName)

    return render_to_response('template.html', {'someForm'    : aForm,
                                                'regularData' : stringData,
                                                'jsonData'    : jsonData...})

utils.py

Contains functions to take the data as a string and return response objects. This part I am unsure if I am doing correctly. I call these functions in the view to get jsonData (and csvData) into their proper formats from the original data string.

def jsonToJsonFile(dataString, fileName):

    #Get the data as json
    theData = json.dumps(dataString)

    #Prepare to return a json file
    response = HttpResponse(theData, mimetype = 'application/json')
    response['Content-Disposition'] = 'attachment; filename=' + str(fileName) + '.json'

    #return the response
    return response 

template.html

I am currently passing the responses into the template. This is where I am really lost, and have not yet begun to find a good solution. I expect I will need to use javascript to return the variables (jsonData and csvData) to the user when the button is clicked. I have attempted the use of the onclick action of the anchor class, and then using javascript to return the django variable of the response - but this really isn't working.

<li class = 'button'>
    <a  href = "#dataButtons" onclick = "javaScript:alert('test');"> 
    TEST
    </a>
</li>
<li class = 'button'>
    <a  href = "#dataButtons"  onclick = "javaScript: var a = '{{ jsonData }}'; return a;"> 
    JSON
    </a>
</li>

I put the test part in there to, well, test whether or no the alert would work. It does. However, when I click the button for the json data, nothing happens.

Am I approaching this completely wrong? Or is there something small that I am missing?

Answer 1

Solution:

After looking at the problem a little further and talking to a colleague about it, it seems as though my problem lies in trying to pass the response object to the javascript. For those interested, I solved the problem with a little careful re-routing of the data.

views.py

In my views.py I added a couple lines of code in my main view that would set variables of two extra views (one for csv one for json) to the response objects holding the data. These two extra views would then be called when their respective buttons were pressed, returning the httpresponse and prompting the user for download.

#MAIN VIEW FUNCTION
def view(request):
    #Do stuff, get data as string

    #Get data into needed formats 
    jsonData  = jsonToJsonFile(dataString, fileName)

    #Set values to external view ****NEW PART****
    returnJSON.jsonData = jsonData

    #Render main template
    return render_to_response('mainTemplate.html', {'someForm'    : aForm,
                                                    'regularData' : dataString})

#SECONDARY VIEW TO RETURN JSON DATA TO USER ****NEW PART****
def returnJSON(request):
    #Simply return the response
    return returnJSON.jsonData

template.html

Then, when the button is pressed by the user, the anchor is linked via the url to the secondary django view that will present the download option to the user.

<li class = 'button'>
    <a  href = "{% url client.views.returnJSON %}"> 
        JSON
    </a>
</li>

urls.py

Lastly, I just pointed my url patterns to the view.

urlpatterns = patterns('',
    (r'^somesite/$', views.view),
    (r'^somesite/json$',  views.returnJSON),
)

So far, this method has worked great for me! If anyone has any other suggestions, or a better method, I would certainly be open to hear it.

Answer 2

I think you need to change your javascript to make it start a file download - see this question & answer: starting file download with JavaScript