Deleting features

We next want to let the user delete an existing feature. To do this, we'll add a Delete Feature button to the "Edit Feature" view. Clicking on this button will redirect the user to the "Delete Feature" view for that feature.

Edit the edit_feature.html template, and add the following highlighted lines to the <form> section of the template:

  <form method="POST" action="">
    <table>
      <tr>
        <td></td>
        <td align="right">
          <input type="submit" name="delete"
                 value="Delete Feature"/>
        </td>
      </tr>
      {{ form.as_table }}
      ...

Notice that we've used <input type="submit"> for this button. This will submit the form with an extra POST parameter named delete. Now, go back to the shapefiles.views module and add the following to the top of the edit_feature() function:

  if request.method == "POST" and "delete" in request.POST:
    return HttpResponseRedirect("/delete_feature/" +
                                shapefile_id+"/"+feature_id)

We next want to implement the "Delete Feature" view. Open the top-level urls.py module and add the following to the list of URL patterns:

url(r'^delete_feature/(?P<shapefile_id>\d+)/(?P<feature_id>\d+)$',
    shapeEditor.shapefiles.views.delete_feature),

Next, create a new file named delete_feature.html in the shapeEditor/shapefiles/templates directory, and enter the following text into this file:

<html>
  <head>
    <title>ShapeEditor</title>
  </head>
  <body>
    <h1>Delete Feature</h1>
    <form method="POST">
      Are you sure you want to delete this feature?
      <p/>
      <button type="submit" name="confirm"
              value="1">Delete</button>
      &nbsp;
      <button type="submit" name="confirm"
              value="0">Cancel</button>
    </form>
  </body>
</html>

This is a simple HTML form that confirms the deletion. When the form is submitted, the POST parameter named confirm will be set to 1 if the user wishes to delete the feature. Let's now implement the view that uses this template. Open the shapefiles.views module and add the following new view function:

def delete_feature(request, shapefile_id, feature_id):
  try:
    feature = Feature.objects.get(id=feature_id)
  except Feature.DoesNotExist:
    return HttpResponseNotFound()

  if request.method == "POST":
    if request.POST['confirm'] == "1":
      feature.delete()
    return HttpResponseRedirect("/edit/" +
                                shapefile_id)

  return render(request, "delete_feature.html")

As you can see, deleting features is quite straightforward.

Table of Contents for Python Geospatial Development - Third Edition

Deleting features

Table of Contents for
Python Geospatial Development - Third Edition