updating attributes in active record - simple q I think!

rubyonrails-talk
1

Hi all,

I have a model Events, with the attributes relating to events, event name / band / date etc, and venue.

I also have a model called venue, and all the different saved venues are presented as a dropdown list when creating a new event.

Attributes associated with the saved venue such as latitude and longitude are then copied over to the event being saved. This works fine.

However when I go back to the saved event and try to update it, if I choose a new venue from the list and press update, the latitude / longitude values aren't getting copied over. I've tried many possible solutions, sometimes with temporary success (on first try), but none of them work continuously, here's what I've tried

<code> EventController

def update

    @event = Event.find(params[:id])     @venue = (Venue.where(:venueName => @event.venue))[0]

   if @venue   @event.city_location = @venue.city_location   @event.longitude = @venue.longitude   @event.latitude = @venue.latitude    end

    if @event.update_attributes(params[:suggested_event])

      flash[:success] = "SuggestedEvent updated."       redirect_to @event

</code>

Values didn't change.

I tried this in the console and got the error

NameError: undefined local variable or method `params' for #<Object:0x100177298>   from (irb):7

and in the console removing the word 'params' seemed to do the trick, so updated the code to <code> ...     if @event.update_attributes(:suggested_event) .... </code>

This worked once, then never again!!!

I've also tried

<code>

    @event = Event.find(params[:id])     @venue = (Venue.where(:venueName => @event.venue))[0]

  if @venue   @event.update_attributes(:city_location => @venue.city_location)   @event.update_attributes(:longitude => @venue.longitude)   @event.update_attributes(:latitude => @venue.latitude)   end

    if @event.update_attributes(params[:suggested_event])

      flash[:success] = "SuggestedEvent updated."       redirect_to @event </code>

but again the values didn't change.

Could anyone please tell me

a - how to update values of active record properly in this case? b - why console doesn't recognise 'params' and c - why on earth might the 2nd try have worked once, and then never again! (unless it was a mirage?!)

Any help massively appreciated

Mike

ps. I deliberately wanted the values to be copied over, so that afterwards I could 'tweak' each event individually, for example by having a very slightly different latitude on multiple events in the same venue means on my google map view of how to get to them, I get multiple pins!!

2

but again the values didn't change.

Could anyone please tell me

a - how to update values of active record properly in this case?

Either params doesn't contain what you think it is and so the call to update_attributes doesn't do anything, or you've got validations preventing the record from saving or you've got some attr_protected/ attr_accessible calls somewhere. Other than that @event.update_attributes(params[:suggested_event]) is fine, as long as params[:suggested_event] contains the right thing.

b - why console doesn't recognise 'params'

because params is an instance method that controllers have. It would be pretty meaningless in the console, since there is no associated request.

and c - why on earth might the 2nd try have worked once, and then never again! (unless it was a mirage?!)

Must have been a mirage - it's completely meaningless.

Fred

3

Ok,

thanks for your help.

so I'm trying to get one of the values out of 'params' before updating the record, and then use the value of the param to change other params before saving the record.

    # the record I'm saving     @event = Event.find(params[:id])

    # look at different model called venue to see if there are any with the same name     @venue = (Venue.where(:venueName => @event.venue))[0]

  # if there are venues of the same name as the event I'm trying to save, copy longitude and latitude values from venue to event.   if @venue   @event.update_attributes(:city_location => @venue.city_location)   @event.update_attributes(:longitude => @venue.longitude)   @event.update_attributes(:latitude => @venue.latitude)   end

  #save the event   if @event.update_attributes(params[:suggested_event])

If I say that the event is at a venue called 'Warehouse 54', I want to go and search all my saved venues looking for 'venue 54', and then filling in other values in the 'event' according to what saved for that venue.

"Either params doesn't contain what you think it is and so the call to update_attributes doesn't do anything," Params doesn't contain what I want it to - it's not going and filling in the other values

Any advice on how to look at, and alter the params being updated before they're updated?

Thanks

4

sorry "looking for 'venue 54'" should read looking for 'Warehouse 54'

5

This seems to be working:

Overwrote the update_attributes method in Events Model.

def update_attributes(attributes)

  venueName = attributes[:venue]   sameVenueName = Venue.where(:venueName => venueName)[0]

  if sameVenueName   attributes[:city_location] = sameVenueName.city_location   attributes[:latitude] = sameVenueName.latitude   attributes[:longitude] = sameVenueName.longitude   end

  self.attributes = attributes   save end

6

Why are you not just saying event belongs_to venue (venue has_many events)? Then you do not need to save the venue lat and long in the event as they will be automatically available as event.venue.latitude for example. If you do not know how to do this have a look at the Rails Guide on ActiveRecord relationships.

Colin

7

Cheers for the tip Colin,

"Why are you not just saying event belongs_to venue (venue has_many events)?"

I'm still learning all the various options, and that sounds very interesting, I'd read about associations, and the reason I didn't use them this time was because I want the ability to be able to 'tweak' the individual values for each event ever so slightly, for example by having a slight variation in longitude / latitude means that events shown on a map are a cluster of pins about the venue, instead of lots of pins on top of one another. Actually, though this could be more effectively implemented with a method for adding random variation, in which case your 'belongs_to - has_many' relationship would actually be very useful.

The other consideration is that I'm downloading the data using xml, I'm unsure if the associated venue data will be downloaded when I retrieve the data about events? Any idea how to do this? or is this completed with

      format.xml { render :xml => @events } ?

cheers,

Mike

8

I have not used render to xml so I don't know how to do it. I can guarantee that it is possible and google shows lots of hits. If you do provide lat and long offsets in the event that are to be added to those of the venue then you will want to provide access methods in the event model so that you can say things like @event.latitude where this is a method of Event that fetches the venue position and adds the offset. You will then presumably need to put that in the xml. A quick bit of googling suggests you might want to use xml builder for this but as I said I have not done such things myself so don't take my word for it.

Colin