MapWarper at Where2.0, with Layers!

Tomorrow I’m going to be doing an Ignite talk about MapWarper, and will talk about the newest function – Layers!

You can now make a mosaic of your maps.

For example, here’s one I made really quickly from some of  Andrew Chadwicks Oxford scanned maps, and dropped into Google Eartyhi

Adding a primary key id to table in rails

Just a quick little tip in case someone searches for it.

I have a table that was used for a has_and_belongs_to_many (habtm) relationship – which was great earlier on. As the application grew, needed to change to a has_many :through (hmt) relationship – using this table as a model etc. Now. initially, I used “:id => false” when creating the habtm join table (Mahmoud tells you why).

But one needs an primary key id on hmt join tables. So created a migration:
def self.up
add_column :table_name, :id, :primary_key

def self.down
remove_column :table_name, :id

And it added an id column to the table in the correct data type (integer) and gave id values to the existing records. sweet.

Also note that you don’t have to give the :id column a datatype, as to rails :primary_key is a datatype.