Pre-selecting ToscaWidgets jqgrid values in TurboGears

My Turbogears project has recently reached an important milestone; one of the back-end processes now runs pretty much continuously and the plugins it use (or at least the ones I can see) are also working.  That means I can turn to the front-end which displays the data the back-end collected.

For some of the data I am using a ToscaWidgets (or TW2) widget called a jqGridWidget which is a very nice jquery device that separates the presentation and data using a json query.  I’ve mentioned previously about how to get a jqGridWidget working but left the pre-filtering out until now.  This meant that my grid showed all the items in the database, not just the ones I wanted to see, but it was a start.

Now this widget displays things called Attributes which are basically children of another model called Hosts. Basically, Attributes are things you want to check or track about a Host.  My widget used to show all Attributes but often on a Host screen, I want to see its hosts only. So, this is how I got my widget to behave; I’m not sure this is THE CORRECT way of doing it, but it does work.

First, in the Hosts controller you need to create the widget and pass along the host_id that the controller has obtained.  I was not able to use the sub-classing trick you see in some TW2 documentation but actually make a widget instance.

class HostsController(BaseController):
    # other stuff here
    class por2(portlets.Portlet):
        title = 'Host Attributes'
        widget = AttributeGrid()
        widget.host_id = host_id

Next, the prepare() method in the Widget needs to get hold of the host_id and put it into the postData list.  I needed to do it before calling super() because the options become one long string in the sub-class.

class AttributeGrid(jqgrid.jqGridWidget):
    def prepare(self, **kw):
        if self.host_id is not None:
            self.options['postData'] = {'hostid': self.host_id}
        super(AttributeGrid, self).prepare()

This means the jqgrid when it asks for its JSON data will include the hostid parameter as well.  We need that method to “see” the host ID so we can filter the database access.

Finally in the JSON method for the Attribute we pick up and filter on the hostid.

    def jqsumdata(self, hostid=0, page=1, rows=1, *args, **kw):
        conditions = []
        if hostid > 0:
            conditions.append(model.Attribute.host_id == hostid)
        attributes =model.DBSession.query(model.Attribute).filter(and_(*conditions))

From there you run through the attributes variable and build your JSON reply.


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