CODEWITHSUNDEEP
ruby-on-railsruby-on-rails-3
HUSTEN
HUSTEN

Reputation: 5197

How can I set "If" statement with nil?

country attribute's default value is nil.

In countries table, some record has image_url, and the rest of the record's country attributes are nil.

So I coded this in helper

def image(user)
    if user.country.image_url
        image_tag "flags/#{user.country.image_url}.png" 
    end
end

However, it returns error when image_url was nil

Something went wrong

How can I fix?

Upvotes: 0

Views: 98

Answers (2)

Noz
Noz

Reputation: 6346

While method chaining like that certainly works, your code will look a lot cleaner and become less coupled if you implement some method delegation.

Inside of your User model:

class User < ActiveRecord::Base

     belongs_to :country

     delegate :image_url, :to => :country, :prefix => true, :allow_nil => true       

end

Now your helper becomes simply:

def image(user)
    if user.country_image_url
        image_tag "flags/#{user.country_image_url}.png" 
    end
end

Law of Demeter states:

Each unit should have only limited knowledge about other units: only units "closely" related to the current unit.

Also check out Rail Best Practices Law of Demeter; if nothing else you're saving yourself the extra clause in your if statement & your code looks pretty.

Upvotes: 3

Xavier Holt
Xavier Holt

Reputation: 14619

You'll need two conditions: The user has to have a country, and that country has to have an image_url. Only then will there be something to show. Luckily, it's a simple tweak:

def image(user)
    if(user.country && user.country.image_url)
        image_tag "flags/#{user.country.image_url}.png" 
    end
end

If you're paranoid, you should make sure that user isn't nil either.

Hope that helps!

Upvotes: 3

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