Rails ActiveRecord Association issue

Question

I've 2 model:

Performance and PerformanceType and 2 respective tables: performances and performance_types.

Into performances there is a foreign key column "performance_type_id".

How I can get the name of performance_type_id from the other table using ActiveRecord Associations?

class Performance < ActiveRecord::Base
has_one :users
has_one :rates
has_one :performace_types
end

class PerformanceType < ActiveRecord::Base
    belongs_to :performances
end

With above code I try to do into console:

myvar = Performance.first
myvar.performance_types
NoMethodError: undefined method `performance_types' for #<Performance:0x007f9694b3e700>

I know that the problem is for my bad interpretation of active record associations, can anyone help me?

regards.

migrations from creating to foreign keys adding...

class CreatePerformances < ActiveRecord::Migration
  def change
    create_table :performances do |t|

      t.timestamps null: false
    end
  end
end

class CreatePerformanceTypes < ActiveRecord::Migration
  def change
    create_table :performance_types do |t|

      t.timestamps null: false
    end
  end
end

class AddPerformanceTypeIdToPerformance < ActiveRecord::Migration
  def change
    add_column :performances, :performance_type_id, :integer
  end
end

class AddAppointmentInfoToPerformance < ActiveRecord::Migration
  def change
    add_column :performances, :user_id, :integer
    add_column :performances, :start_at, :datetime
    add_column :performances, :end_at, :datetime
  end
end

class AddUserToPerformances < ActiveRecord::Migration
  def change
    add_foreign_key :performances, :users
  end
end

class AddTypeToPerformances < ActiveRecord::Migration
  def change
    add_foreign_key :performances, :performance_types
  end
end

class AddAdditionalFieldsToPerformanceType < ActiveRecord::Migration
  def change
    add_column :performance_types, :name, :string
    add_column :performance_types, :description, :string
  end
end

class AddPerformanceTypeToRate < ActiveRecord::Migration
  def change
    add_foreign_key :rates, :performance_types
  end
end

class AddRateToPerformances < ActiveRecord::Migration
  def change
    add_column :performances, :rate_id, :integer
    add_foreign_key :performances, :rates
  end
end

It should be singular, not plural. has_one :performance_type You've also misspelt performance - might be just when typing your question though — j-dexx
– j-dexx, Commented Jun 9, 2016 at 16:13

Ursus · Accepted Answer · 2016-06-09 18:04:30Z

4

has_one and belongs_to refer to a single object so you should use singularized form

class Performance < ActiveRecord::Base
    has_one :users
    has_one :rates
    has_one :performance_type
end

class PerformanceType < ActiveRecord::Base
    belongs_to :performance
end

edited Jun 9, 2016 at 18:04

answered Jun 9, 2016 at 16:13

Ursus

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1 Comment

user3720516 Over a year ago

Not sure why this answer is being upvoted; the has_one associations are still plural, the "has_one :perfomace_type" is misspelled, and there is no mention of the migration files (so how do we know he actually setup the association the correct way?)

John Murphy · Accepted Answer · 2016-06-09 18:29:27Z

1

I think that this is what you want. The foreign key performance_type_id remains in performances. You have many performances with the same performance type, but each performance has only one performance type.

class Performance < ActiveRecord::Base 
  # note performance type is singular
  belongs_to :performance_type
end

class PerformanceType < ActiveRecord::Base
  has_many :performances 
end

p = Performance.first
# this should work 
p.performance_type

answered Jun 9, 2016 at 18:29

John Murphy

763 bronze badges

1 Comment

michael Over a year ago

Doesn't work NoMethodError: undefined method `performance_type' for #<Performance:0x007fcf75a893b8>

user3720516 · Accepted Answer · 2016-06-09 16:15:11Z

0

You should change your Performance class listing the "has_one" relationship with the singular model (not plural):

class Performance < ActiveRecord::Base
  has_one :user
  has_one :rate
  has_one :performance_type
end

class PerformanceType < ActiveRecord::Base
  belongs_to :performance
end

It's also important that your migration file is correctly configured, too:

class CreatePerformances < ActiveRecord::Migration
  def change
    create_table :performances do |t|
    end

    create_table :performance_types do |t|
      t.belongs_to :performance, index: true
      t.belongs_to :rate
      t.belongs_to :user
    end
  end
end

answered Jun 9, 2016 at 16:15

user3720516

8 Comments

michael Over a year ago

Ok, now the associations are in singular form... The tables are or because I have correctly created the FK to the 3 tables. Now how access to performance_types column with ruby notation?

michael Over a year ago

Ehm, doesnt work. How access to other columns by the association?

user3720516 Over a year ago

Can you post your migration file?

user3720516 Over a year ago

Whoa, OK. Looks like you've been doing a lot of migrations for this. It's a bit hard for me to follow. Could you post your schema.rb file?

Cyzanfar Over a year ago

@Tommyixi do your research, what you are saying is WRONG. has_one association are singular. downvoted.

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