ftw.geo 1.1

Automatically geocoding your content types

In order for your content types to be automatically geocoded on ObjectEdited or ObjectInitialized events, you need to create an adapter for your content type that implements IGeocodableLocation and knows how to build a geocodable location string from the content type’s location related fields.

In order to implement the interface you need to define a getLocationString method on your adapter that returns the complete location as a comma separated string, with the location parts getting less specific from left to right.

For example:

'1600 Amphitheatre Parkway, Mountain View, CA, US'
'Engehaldestr. 53, 3012 Bern, Switzerland'

If the getLocationString method returns the empty string or None, the event handler won’t attempt to do a geocode lookup, so this is the suggested way to abort geocoding if not enough location information is available.

Example code:

from ftw.geo.interfaces import IGeocodableLocation
from zope.component import adapts
from zope.interface import implements


class MyTypeLocationAdapter(object):
    """Adapter that is able to represent the location of an MyType in
    a geocodable string form.
    """
    implements(IGeocodableLocation)
    adapts(IMyType)

    def __init__(self, context):
        self.context = context

    def getLocationString(self):
        """Build a geocodable location string from the MyType's address
        related fields.
        """
        street = self.context.getAddress()
        zip_code = self.context.getZip()
        city = self.context.getCity()
        country = self.context.getCountry()

        location = ', '.join([street, zip_code, city, country])
        return location

Register the adapter with ZCML:

<adapter
    factory=".mytpe.MyTypeLocationAdapter"
    />

Caching of geocoding responses

Responses from the geocoding API are being RAM cached. The cache key being used is the result of the getLocationString method, which means that for every unique location string the geocoding lookup is only done once and subsequently fetched from the cache.

Only triggering geocoding when location fields changed

If we were to do a geocode lookup on every ObjectEdited event, any custom coordinates that have been set would be overriden every time any field on the content item is changed (even if the geocoding response itself was fetched from the cache).

To avoid this, ftw.geo stores the result of getLocationString as an annotation on the object and on ObjectEdited checks if the location string (and therefore the location related fields) actually changed, and only does the lookup when necessary. This means:

On ObjectInitialized the content type will first be geocoded initally (unless getLocationString returned None or the empty string). If you manually set coordinates after that through the ‘Coordinates’ tab provided by collective.geo.contentlocations they will be saved and overwrite the coordinates determined previously by geocoding. After that, if you edit the content item and change any fields not related to the location, the custom coordinates will be preserved. Only if you change one of the location related fields used in getLocationString the geocoding will be performed again and any custom coordinates overwritten.

Google API Key

Google’s geocoding API can be used without an API Key, but then is limited to 2500 requests per day. If you defined your Google Maps API Key in collective.geo.settings it will be used, otherwise the geocoding API will be called without an API key.

Rendering a content map viewlet in a custom template

If you don’t want your content map displayed in one of the default viewlet managers (plone.abovecontentbody / plone.abovecontentbody) on the content item’s main view but instead in a custom view and/or a different viewlet manager, this is how you do it:

First, you need to make sure your browser view implements a specific interface and provide a KMLMapViewletLayer adapter (view, request, context, widget) for it:

<adapter
    for="..interfaces.IContactView
         zope.interface.Interface
         zope.interface.Interface
         zope.interface.Interface"
    factory="collective.geo.kml.browser.viewlets.KMLMapViewletLayers"
    />

Then, in your view’s template, simply use the macros provided by collective.geo.mapwidget:

<div id="kml-content-viewlet">
  <metal:use use-macro="context/@@collectivegeo-macros/openlayers" />
  <metal:use use-macro="context/@@collectivegeo-macros/map-widget" />
</div>

1.1 (2013-04-03)

• Use message IDs and defaults in error message translations. [lgraf]

• Improved exception handling when doing geocoding on save. Deal with network errors and any other unhandled exception, and display meaningful messages for all cases. [lgraf]

• Fix tests according to the new features [mathias.leimgruber]

• Display a status message when automatic geocoding didn’t yield any results. [lgraf]

• Make sure to import exceptions we check for from the googlev3 geocoder after switching to V3 geocoding API. [lgraf]

• Deal with multiple results for automatic geocoding. When automatic geocoding on save for a content item results in more than one match, choose the first one and display a message to the user that he might want to change it. [lgraf]

• Remove api key usage. The geopy GoogleV3 Geocoder does not implement an api key. [mathias.leimgruber]

• Use google map api V3 of geopy 0.95. See -> http://plone.293351.n2.nabble.com/collective-geo-GBadKeyError-when-geocoding-w-geopy-td7563845.html [mathias.leimgruber]

1.0 (2012-12-03)

• Added import step to uninstall Products.Maps using quickinstaller. [lukasg]

• First implementation. [lukasg]