Ruby-on-rails – How to create has_and_belongs_to_many associations in Factory girl

associationsfactory-bothas-and-belongs-to-manyruby-on-rails

Given the following

class User < ActiveRecord::Base
  has_and_belongs_to_many :companies
end

class Company < ActiveRecord::Base
  has_and_belongs_to_many :users
end

how do you define factories for companies and users including the bidirectional association? Here's my attempt

Factory.define :company do |f|
  f.users{ |users| [users.association :company]}
end

Factory.define :user do |f|
  f.companies{ |companies| [companies.association :user]}
end

now I try

Factory :user

Perhaps unsurprisingly this results in an infinite loop as the factories recursively use each other to define themselves.

More surprisingly I haven't found a mention of how to do this anywhere, is there a pattern for defining the necessary factories or I am doing something fundamentally wrong?

Best Answer

Here is the solution that works for me.

FactoryGirl.define do

  factory :company do
    #company attributes
  end

  factory :user do
   companies {[FactoryGirl.create(:company)]}
   #user attributes
  end

end

if you will need specific company you can use factory this way

company = FactoryGirl.create(:company, #{company attributes})
user = FactoryGirl.create(:user, :companies => [company])

Hope this will be helpful for somebody.

Related Solutions

Ruby-on-rails – How to understand nil vs. empty vs. blank in Ruby

.nil? can be used on any object and is true if the object is nil.

.empty? can be used on strings, arrays and hashes and returns true if:

String length == 0
Array length == 0
Hash length == 0

Running .empty? on something that is nil will throw a NoMethodError.

That is where .blank? comes in. It is implemented by Rails and will operate on any object as well as work like .empty? on strings, arrays and hashes.

nil.blank? == true
false.blank? == true
[].blank? == true
{}.blank? == true
"".blank? == true
5.blank? == false
0.blank? == false

.blank? also evaluates true on strings which are non-empty but contain only whitespace:

"  ".blank? == true
"  ".empty? == false

Rails also provides .present?, which returns the negation of .blank?.

Array gotcha: blank? will return false even if all elements of an array are blank. To determine blankness in this case, use all? with blank?, for example:

[ nil, '' ].blank? == false
[ nil, '' ].all? &:blank? == true

Ruby-on-rails – Rails: How to rename a database column in a Ruby on Rails migration

rename_column :table, :old_column, :new_column

You'll probably want to create a separate migration to do this. (Rename FixColumnName as you will.):

script/generate migration FixColumnName
# creates  db/migrate/xxxxxxxxxx_fix_column_name.rb

Then edit the migration to do your will:

# db/migrate/xxxxxxxxxx_fix_column_name.rb
class FixColumnName < ActiveRecord::Migration
  def self.up
    rename_column :table_name, :old_column, :new_column
  end

  def self.down
    # rename back if you need or do something else or do nothing
  end
end

For Rails 3.1 use:

While, the up and down methods still apply, Rails 3.1 receives a change method that "knows how to migrate your database and reverse it when the migration is rolled back without the need to write a separate down method".

See "Active Record Migrations" for more information.

rails g migration FixColumnName

class FixColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

If you happen to have a whole bunch of columns to rename, or something that would have required repeating the table name over and over again:

rename_column :table_name, :old_column1, :new_column1
rename_column :table_name, :old_column2, :new_column2
...

You could use change_table to keep things a little neater:

class FixColumnNames < ActiveRecord::Migration
  def change
    change_table :table_name do |t|
      t.rename :old_column1, :new_column1
      t.rename :old_column2, :new_column2
      ...
    end
  end
end

Then just db:migrate as usual or however you go about your business.

For Rails 4:

While creating a Migration for renaming a column, Rails 4 generates a change method instead of up and down as mentioned in the above section. The generated change method is:

$ > rails g migration ChangeColumnName

which will create a migration file similar to:

class ChangeColumnName < ActiveRecord::Migration
  def change
    rename_column :table_name, :old_column, :new_column
  end
end

Best Answer

Related Solutions

Ruby-on-rails – How to understand nil vs. empty vs. blank in Ruby

Ruby-on-rails – Rails: How to rename a database column in a Ruby on Rails migration

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