Beginning Google Maps Applications

Rails 2 changed the way to_json works on ActiveRecord objects. Prior to Rails 2, to_json returned a hash of hashes — the first level hash had the key ‘attributes’, which in turn had another hash with your field name/values.

With Rails 2, calling to_json on an AR object just gives you a hash of field name/values. The new way is easier and more intuitive. However, in breaks our code in places where we use to_json to pass AR data into JavaScript.

The changes are straightforward. There were two ways we dealt with the intermediate “attributes” hash prior to Rails 2:

1. we used map/collect before calling to_json, i.e.: cities.collect{|c|c.attributes}.to_json
2. we dealt with ‘attributes’ in JavaScript, i.e., var marker=markers[i].attributes

Fixing it just means removing references to the ‘attributes’ and using the ActiveRecord instance directly.

Here are all the places changes need to be made:

• 3.8: var marker=markers[i].attributes to var marker=markers[i]
• 4.6: all instances of result.attributes to just result
• 4.15: var stores=<%=(@stores.collect {|s|s.attributes}).to_json%>; to var stores=<%=@stores.to_json%>;
• 5-12: remove the to_json method from class Tower
• 7-2: render :text=>cities.collect{|c|c.attributes}.to_json to render :text=>cities.to_json
• 7-5: render :text=>cities.collect{|c|c.attributes}.to_json to render :text=>cities.to_json
• 7.15: var points=<%=@towers.collect{|c|c.attributes}.to_json %>; to var points=<%=@towers.to_json %>;