CODEWITHSUNDEEP
ruby-on-rails-3
Gediminas Šukys
Gediminas Šukys

Reputation: 7391

Check nil values in .map method

When User object is nil, which is defined in belongs_to association, I get an error: p.user.title is nil.

How to check that p.user or p.user.title is defined in .map to avoid an error?

@posts = Post.all 
results = @posts.map { |p| 
{ 
  :id => p.id,
  :text => p.text,
  :user_title => p.user.title
}
}

Upvotes: 0

Views: 640

Answers (3)

Rob Di Marco
Rob Di Marco

Reputation: 44982

You can use the try method. This will return nil if the user is nil

@posts = Post.all 
results = @posts.map { |p| 
    { 
      :id => p.id,
      :text => p.text,
      :user_title => p.user.try(:title)
    }
}

Upvotes: 1

Frans
Frans

Reputation: 1448

Easy as pie.

p.user.try(:title)

The above runs #title on user if user is not nil.

Upvotes: 2

Chowlett
Chowlett

Reputation: 46675

Simple - just test p.user before you access title:

@posts = Post.all 
results = @posts.map do |p| 
  { 
    :id => p.id,
    :text => p.text,
    :user_title => p.user && p.user.title
  }
end

results[i][:user_title] will then be nil if either p.user or p.user.title was.

Upvotes: 1

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