Basic Rails problem with has_many nil values and permalinks

rubyonrails-talk
1

Hi,

I have a model property with has_many. I find the property and then I need to find the name of the building or the neighborhood that the property belongs to. The property is not always assigned a building or neighborhood.

This becomes a problem when createing permalinks with permalink_fu.

has_permalink [:neighborhood_name, :building_name, :address]

The neighborhood name and building name are defined here in property.rb

  def neighborhood_name       neighborhood.name   end

  def building_name        building.name   end

If the property does not have a neighborhood or a building, then I get an error: The error occurred while evaluating nil.name):   app/models/property.rb:425:in `neighborhood_name'

I know that I'm missing something really basic in Rails. Can someone help me out so that it generates the permalink even if the neighborhood or building are empty?

Thanks.

2

You could just test neighborhood and building in your _name methods and return an appropriate default if nil.

Colin

3

Cs Webgrl wrote:

Colin Law wrote:

You could just test neighborhood and building in your _name methods and return an appropriate default if nil.

Thanks for your reply. I don't mean to make you do all of the work, but I can't seem to find the correct syntax to go with this to make it pass correctly? Everything I put into the _name methods is ignored and I still get an error.

What are you putting into those methods? Instead of asking for our code, show us yours.

Thanks for your help.

Best,

4

You have snipped the original. I don't know whether has_permalink is happy with nil parameters, if so then you could just do

def neighborhood_name      neighborhood.name if neighborhood end

This will return nil if neighborhood is nil. If you need a default name however then something like

def neighborhood_name      neighborhood ? neighborhood.name : 'default_name' end

If Marnen reads this he will tell you (and probably me) in no uncertain terms to read up on basic Ruby coding :slight_smile:

Colin

5

Colin Law wrote:

still get an error.

You have snipped the original. I don't know whether has_permalink is happy with nil parameters, if so then you could just do

def neighborhood_name      neighborhood.name if neighborhood end

This will return nil if neighborhood is nil. If you need a default name however then something like

def neighborhood_name      neighborhood ? neighborhood.name : 'default_name' end

Yeah, that's about what I was thinking.

If Marnen reads this he will tell you (and probably me) in no uncertain terms to read up on basic Ruby coding :slight_smile:

Good God, am I becoming a List Personality [TM]? :slight_smile:

You're right, I'd recommend that the OP brush up on basic Ruby. For you, I'd simply recommend not spoon-feeding...

Colin

Best,

6

I think sometimes a modicum of spoon feeding is helpful to get people over immediate problems, this combined with hints as to where to go next. In this case I bounced the hint off you so I looked like the nice guy :slight_smile:

Somehow this thread seems to have got split, for me anyway. Your replies are appearing on a different thread to the original.

Colin

7

Colin Law wrote:

I think sometimes a modicum of spoon feeding is helpful to get people over immediate problems, this combined with hints as to where to go next. In this case I bounced the hint off you so I looked like the nice guy :slight_smile:

Thank you for the information. Yes, I need to read up on some basic Ruby. I was thinking that I needed to do neighborhood.<something> and not just neighborhood which is why I was unsuccessful. Back to reading. I have the David Black's Ruby for Rails book along with the Pick axe book and AWD. If there's another resource that you recommend, please let me know.