CODEWITHSUNDEEP
ruby-on-rails-3activerecordhas-many-through
blackst0ne
blackst0ne

Reputation: 721

Ruby on Rails: how to work with multiple models and has_many through relationship?

I can't solve my problem for already a week.

I have 4 models: Person, Position, Workspace, and Phonenumber.

The hierarchy is Person > Position > Workspace > Phonenumber.

A chain of all 4 models is unique. Say, there may be only one man:

Person | Position | Workspace   | Phonenumber |
Smith    Engineer  Department #4    555-666

But there may be another man with the same Position, Workspace, and Phonenumber:

Person | Position | Workspace     | Phonenumber |
Johnson  Engineer   Department #4     555-666

Or even the same Mr. Smith, but different position or workspace.

Person | Position | Workspace     | Phonenumber |
Smith    Engineer   Department #7     555-666

And so on.

All 4 at the same time are unique.

I want to store this data. I tried many different things. Nothing helped me at 100%. For now my best idea is to use has_many through relationships with join model called Employee:

person_id | position_id | workspace_id | phonenumber_id

But how do I work with data?

Say, I want to create new person with some position, workspace and phonenumber. How do I do that?

Upvotes: 1

Views: 815

Answers (1)

wintermeyer
wintermeyer

Reputation: 8318

To create your setup in a Rails 4 application:

rails g model Person last_name
rails g model Position job_title
rails g model Workspace name
rails g model Phonenumber number
rails g model Employee person_id:integer position_id:integer workspace_id:integer phonenumber_id:integer

app/models/person.rb

class Person < ActiveRecord::Base
  has_many :employees, :dependent => :destroy

  has_many :positions, :through => :employees
  has_many :workspaces, :through => :employees
  has_many :phonenumbers, :through => :employees

  validates :last_name, 
            :presence => true  
end

app/models/employee.rb

class Employee < ActiveRecord::Base
  belongs_to :person
  belongs_to :position
  belongs_to :workspace
  belongs_to :phonenumber

  validates :person, :position, :workspace, :phonenumber, 
            :presence => true

  validates :person_id,
            :presence => true,
            :uniqueness => { :scope => [ :position_id, :workspace_id, :phonenumber_id ]}
end

Now to create a new Person with everything:

Person.create(:last_name => 'Smith').employees.where(:position => Position.where(:job_title => 'Engineer').first_or_create, :workspace => Workspace.where(:name => 'Department #8').first_or_create, :phonenumber => Phonenumber.where(:number => '555-666').first_or_create).first_or_create

To create an other Position for this Smith:

Person.where(:last_name => 'Smith').last.employees.where(:position => Position.where(:job_title => 'Admin').first_or_create, :workspace => Workspace.where(:name => 'Department #8').first_or_create, :phonenumber => Phonenumber.where(:number => '555-667').first_or_create).first_or_create

first_or_create searches for the entry or creates a new one.

Upvotes: 1

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