CODEWITHSUNDEEP
ruby-on-railsinheritanceabstract-classruby-on-rails-5
Suthan Bala
Suthan Bala

Reputation: 3299

Rails 5 Model not inheriting the parent's methods

I have the ApplicationRecord model as follows:

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true

  def hello_world
    return "helllloo"
  end
end

and I have Instance model as follows:

class Instance < ApplicationRecord

end

Then I have the controller trying to run the hello_world, but it's throwing the following error saying hello_world method is not available.

Controller

class InstancesController < ApplicationController
  before_action :set_instance, only: [:show, :update, :destroy]

  # GET /instances
  def index
    @instances = Instance.all
    return render(:json => {:instances => @instances, :hi_message => Instance.hello_world})
  end
end

Error

{
  "status": 500,
  "error": "Internal Server Error",
  "exception": "#<NoMethodError: undefined method `hello_world' for #<Class:0x00000009b3d4a0>>",
  "traces": {
    "Application Trace": [
      {
        "id": 1,
        "trace": "app/controllers/instances_controller.rb:7:in `index'"
      }
    ],.....

Any idea why it's not inheriting the methods?

**Note: ** I am running the app in API mode.

Upvotes: 1

Views: 708

Answers (1)

Deepak Mahakale
Deepak Mahakale

Reputation: 23661

One point to mention here is hello_world is instance method and you are calling it on a class instead of instance

Solution 1:

Change the method to class method

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true

  def self.hello_world
    return "helllloo"
  end
end

and

Instance.hello_world
#=> "helllloo"

Solution 2:

Call the method on instance 

class ApplicationRecord < ActiveRecord::Base
  self.abstract_class = true

  def hello_world
    return "helllloo"
  end
end

and

Instance.new.hello_world
#=> "helllloo"

# OR

instance = Instance.new
instance.hello_world
#=> "helllloo"

Upvotes: 2

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