Build associated model confusion

rubyonrails-talk
1

I'm new to Rails3, and I'm just trying to get one last thing to work before I call it a night. The situation is the following (please if the code is horrible, just let me know, still learning):

I want to log a dive. I might have a new location on that dive at which point I have to create a new Location, and then create the dive. A dive has_one location. A location has_many dives. Currently the foreign key is on dive as location_id.

How do I properly, in my dives_controller, generate the location, get the ID, and pass it on to my new dive? It would be nice to have the constructor of Location called, but if it doesn't work that way, then that's okay too.

My code is below:

Thanks.

2

Melih Onvural wrote in post #968249:

I'm new to Rails3, and I'm just trying to get one last thing to work before I call it a night. The situation is the following (please if the code is horrible, just let me know, still learning):

I want to log a dive. I might have a new location on that dive at which point I have to create a new Location, and then create the dive. A dive has_one location. A location has_many dives. Currently the foreign key is on dive as location_id.

Then Dive belongs_to Location. Go review the difference between belongs_to and has_one.

Best,

3

A bit closer now. I now have it such that:

dive     belongs_to :location end

I've got the initialize function following through, but it's still throwing an error on this code here:

    @location = @dive.create_location(params[:location])

    @dive.location_id = @location.id

with the following error message:

"You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil.delete"

any clues?

4

A comment about your Location model:

You rarely need 'initialize' when creating new model instances (and in this case you don't). The beauty of ActiveRecord is that it automagically gives you instance variables for all table columns. If you need any variables that are not a table column use attr_accessor :foo_bar

Also, for all geocoding needs I would use http://geokit.rubyforge.org/

class Location < AR

  has_many :dives

  before_validation :geocode # or before_save/before_create, your call

  def geocode     # call geokit to do the geocoding   end

end

Hope this helps!

Simon

5

Simon Baumgartner wrote in post #968527:

A comment about your Location model:

You rarely need 'initialize' when creating new model instances (and in this case you don't).

Good catch! But make that "never", not "rarely". ActiveRecord constructors generally shouldn't be overridden. Instead, use before_ or after_create callbacks to set values (as in your example).

The beauty of ActiveRecord is that it automagically gives you instance variables for all table columns. If you need any variables that are not a table column use attr_accessor :foo_bar

Also, for all geocoding needs I would use http://geokit.rubyforge.org/

Indeed. Also investigate Spatial Adapter, and consider PostGIS if you're using PostgreSQL. (If you're not using PostgreSQL, you probably should be. :slight_smile: )

Best,

6

Thanks you guys!

Got things working, but having some problems with GeoKit and Rails3. I'll have to do some more investigation on that front!