Avoiding Nil errors

rubyonrails-talk
1

How do I suppress the nil errors in ActionView Erb templates?

For instance if I have a record in the database table that allows null fields and then I show the record, in this case an association using belongs_to, how do I suppress the Nil errors on those fields that are null?

Thanks, Phill

2

If I am understanding your question correctly, this may help:

<%= event.category? event.category.name : 'No Category Set' %>

-Bradly

3

Thanks. That is what I'm looking for. I was wondering though if there was an simpler / cleaner way than if statements though.

Thanks again,

phill

Bradly wrote:

4

<%= event.category.name rescue 'No Category Set' %>

5

also works:

<%= event.category.name || "default" %>

6

I’ve already used all the different ways described in previous messages, but there has to be a way of setting a global replacement string. My views are just littered with code like that and it doesn’t look nice. A helper might probably help, but even that adds code to every value in the view.

Best regards

Peter De Berdt

7

Hey,

As has already been pointed out, you can use 'rescue', however I find
that the Law of Demeter [1] helps here.

class Event < ActiveRecord::Base    belongs_to :category

   def category_name      self.category and self.category.name or "No Category Name"    end end

<%= event.category_name %>

Another option is to declare a helper method:

def event_category_name(event)    event.category and event.category.name or "No Category Name" end

<%= event_category_name(event) %>

And finally, if (for example) the event's 'name' is always the
category's name then you can use delegate():

class Event < ActiveRecord::Base    belongs_to :category    delegate :name, :to => '(self.category or return "No Category Name")' end

<%= event.name %>

Hope this helps, Trevor

[1] Law of Demeter: Principle of Least Knowledge