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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, OPENSTREETMAP, NASA_GLOBAL_MOSAIC, 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.

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 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 http://rubyforge.org/projects/map-layers/ or send a mail to pka[at]sourcepole[dot]ch.

Copyright © 2008 Pirmin Kalberer, Sourcepole AG