MapLayers plugin for Rails
MapLayers makes it easy to integrate a dynamic map in a Rails application. It can display map tiles and markers loaded from many different data sources. The included map viewer is OpenLayers. With MapLayers you can display and publish ActiveRecord models with geographic data.
Getting Started
Install the latest version of the plugin:
./script/plugin install git://github.com/pka/map_layers.git
Create a controller and a view
./script/generate controller Map index
Initialization of the map
Add the map viewer initialization to the index action in the controller:
@map = MapLayers::Map.new("map") do |map, page|
page << map.add_layer(MapLayers::GOOGLE)
page << map.zoom_to_max_extent()
end
Add this to the head of your view:
<%= map_layers_includes :google => "ABQIAAAA3HdfrnxFAPWyY-aiJUxmqRTJQa0g3IQ9GZqIMmInSLzwtGDKaBQ0KYLwBEKSM7F9gCevcsIf6WPuIQ" %>
Put a map in the body your view:
<div id="map" style="width: 512px; height: 256px;"></div>
<%= @map.to_html %>
Test your basic map with http://localhost:3000/map
Multiple layers
Add a second layer and some more controls in the controller action:
@map = MapLayers::Map.new("map") do |map, page|
page << map.add_layer(MapLayers::GOOGLE)
page << map.add_layer(MapLayers::YAHOO_HYBRID)
page << map.add_control(Control::LayerSwitcher.new)
page << map.add_control(Control::Permalink.new('permalink'))
page << map.add_control(Control::MousePosition.new)
page << map.zoom_to_max_extent()
end
Add the Yahoo Javascript library to the includes:
<%= map_layers_includes :google => "ABQIAAAA3HdfrnxFAPWyY-aiJUxmqRTJQa0g3IQ9GZqIMmInSLzwtGDKaBQ0KYLwBEKSM7F9gCevcsIf6WPuIQ", :yahoo => "euzuro-openlayers" %>
There are many more predefined layer types available: GOOGLE_SATELLITE, GOOGLE_HYBRID, GOOGLE_PHYSICAL, VE_ROAD, VE_AERIAL, VE_HYBRID, YAHOO, YAHOO_SATELLITE, YAHOO_HYBRID, MULTIMAP, OSM_MAPNIK, OSM_TELASCIENCE, GEOPOLE_OSM, NASA_GLOBAL_MOSAIC, BLUE_MARBLE_NG, WORLDWIND, WORLDWIND_URBAN, WORLDWIND_BATHY
To include all Javascript APIs, insert your API keys in the following statement:
<%= map_layers_includes :google => "ABQIAAAA3HdfrnxFAPWyY-aiJUxmqRTJQa0g3IQ9GZqIMmInSLzwtGDKaBQ0KYLwBEKSM7F9gCevcsIf6WPuIQ", :multimap => "metacarta_04", :virtualearth => true, :yahoo => "euzuro-openlayers" %>
Updating the map
Now we want to add some simple markers in an Ajax action. First we add a link in the view:
<%= link_to_remote "Add marker", :url => { :action => "add_marker" } %>
This requires including the prototype library:
<%= javascript_include_tag 'prototype' %>
Then we include a marker layer in the map. Put this after the add_layer statements in the controller:
page.assign("markers", Layer::Markers.new('Markers'))
page << map.addLayer(:markers)
and then we implement the Ajax action:
def add_marker
render :update do |page|
@markers = JsVar.new('markers')
page << @markers.add_marker(OpenLayers::Marker.new(OpenLayers::LonLat.new(rand*50,rand*50)))
end
end
For accessing the marker layer in the Ajax action, we declare a Javascript variable with page.assign
and access the variable later with the JsVar
wrapper.
OpenStreetMap in WGS84
To overlay data in WGS84 projection you can use a customized Open Street Map:
@map = MapLayers::Map.new("map") do |map, page|
page << map.add_layer(MapLayers::GEOPOLE_OSM)
page << map.zoom_to_max_extent()
end
Publish your own data
Create a model:
./script/generate model --skip-timestamps --skip-fixture Place placeName:string countryCode:string postalCode:string lat:float lng:float
rake db:migrate
Import some places:
./script/runner "Geonames::Postalcode.search('Sidney').each { |pc| Place.create(pc.attributes.slice('placeName', 'postalCode', 'countryCode', 'lat', 'lng')) }"
Add a new controller with a map_layer:
class PlacesController < ApplicationController
map_layer :place, :text => :placeName
end
And add a layer to the map:
page << map.addLayer(Layer::GeoRSS.new("GeoRSS", "/places/georss"))
Other types of served layers:
page << map.add_layer(Layer::GML.new("Places KML", "/places/kml", {:format=> JsExpr.new("OpenLayers.Format.KML")}))
page << map.add_layer(Layer::WFS.new("Places WFS", "/places/wfs", {:typename => "places"}, {:featureClass => JsExpr.new("OpenLayers.Feature.WFS")}))
Spatial database support
Using a spatial database requires GeoRuby and the Spatial Adapter for Rails:
sudo gem install georuby
ruby script/plugin install svn://rubyforge.org/var/svn/georuby/SpatialAdapter/trunk/spatial_adapter
Install spatial functions in your DB (e.g. Postgis 8.1):
DB=map_layers_dev
createlang plpgsql $DB
psql -d $DB -q -f /usr/share/postgresql-8.1-postgis/lwpostgis.sql
Create a model:
./script/generate model --skip-timestamps --skip-fixture WeatherStation name:string geom:point
rake db:migrate
Import some weather stations:
./script/runner "Geonames::Weather.weather(:north => 44.1, :south => -9.9, :east => -22.4, :west => 55.2).each { |st| WeatherStation.create(:name => st.stationName, :geom => Point.from_x_y(st.lng, st.lat)) }"
Add a new controller with a map_layer:
class WeatherStationsController < ApplicationController
map_layer :weather_stations, :geometry => :geom
end
And add a WFS layer to the map:
page << map.add_layer(Layer::WFS.new("Weather Stations", "/weather_stations/wfs", {:typename => "weather_stations"}, {:featureClass => JsExpr.new("OpenLayers.Feature.WFS")}))
License
The MapLayers plugin for Rails is released under the MIT license.
Support
For any questions, enhancement proposals, bug notifications or corrections visit rubyforge.org/projects/map-layers/ or send a mail to pka[at]sourcepolech.
Copyright © 2008 Pirmin Kalberer, Sourcepole AG