CODEWITHSUNDEEP
ruby-on-railsruby
0xSina
0xSina

Reputation: 21553

ActiveRecord custom attributes

How can I assign a custom attribute to an ActiveRecord model? For example, I can do it when querying via:

  select("(CASE WHEN wishlist_items.id IS null THEN 0 ELSE 1 END) AS is_wishlisted_by_me").

This adds a custom is_wishlisted_by_me attribute. But what if I already have an instance of an AR model and I want to do:

model.is_wishlisted_by_me = true

this returns a NoMethodError: undefined method

NoMethodError: undefined method `is_wishlisted_by_me=' for #<SIImage:0x007fc8c41c7ef8>
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/activemodel-3.2.13/lib/active_model/attribute_methods.rb:407:in `method_missing'
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/activerecord-3.2.13/lib/active_record/attribute_methods.rb:149:in `method_missing'
    from (irb):8
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/railties-3.2.13/lib/rails/commands/console.rb:47:in `start'
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/railties-3.2.13/lib/rails/commands/console.rb:8:in `start'
    from /Users/Test/.rvm/gems/ruby-1.9.3-p327/gems/railties-3.2.13/lib/rails/commands.rb:41:in `<top (required)>'
    from script/rails:6:in `require'
    from script/rails:6:in `<main>'

Upvotes: 0

Views: 2757

Answers (2)

Michael
Michael

Reputation: 12011

This is what I've done:

after_initialize do
  self.is_wishlisted_by_me = nil unless @attributes.key?("is_wishlisted_by_me")
end

def is_wishlisted_by_me
  @attributes["is_wishlisted_by_me"]
end

def is_wishlisted_by_me=(value)
  @attributes["is_wishlisted_by_me"] = value
end

Upvotes: 0

Henry
Henry

Reputation: 1055

I think you can do it with this way, define attr_accessible in your model:

attr_accessible :user_count

r = User.find_by_sql("select count(*) as user_count from users")

puts r.first.user_count

If a hash will do for you, you may try 

User.connection.select_all("select count(*) as user_count from users")

which will return an array of hash like [{:user_count => 1}]

Upvotes: 1

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