Ruby on rails: Creating a model entry with a belongs_to association

问题

I am trying to add a new entry in my database for a model that has a belongs_to relationship. I have 2 models, Jobs and Clients.

It was easy enough to find tutorial on how to set up the association between these two (using has_many and belongs_to), but I can't seem to find any examples where the association is actually used.

In my code, I am trying to create a new job for the first client. The jobs model has an attribute for client_id, and I know I can probably just manually fill the attribute, but there has to be some ruby convention to easily accomplish this.

Job.create(:client_id => 1, :subject => "Test", :description => "This is a test")

I can easily put that in my code, but I feel like ruby has a better way to do this. Here is the way my models are setup

class Job < ActiveRecord::Base
  attr_accessible :actual_time, :assigned_at, :client_id, :completed_at, :estimated_time, :location, :responded_at, :runner_id, :status, :subject, :description
  belongs_to :client
end

class Client < User
    has_many :jobs
end

class User < ActiveRecord::Base
  attr_accessible :name, :cell, :email, :pref

end

回答1:

Just call create on the jobs collection of the client:

c = Client.find(1)
c.jobs.create(:subject => "Test", :description => "This is a test")

回答2:

You can pass the object as argument to create the job:

client = Client.create
job = Job.create(client_id: client.id, subject: 'Test', description: 'blabla')

The create method will raise an error if the object is not valid to save (if you set validations like mandatory name, etc).

回答3:

Pass the object itself as an argument, instead of passing its ID. That is, instead of passing :client_id => 1 or :client_id => client.id, pass :client => client.

client = Client.find(1)
Job.create(:client => client, :subject => "Test", :description => "This is a test")

回答4:

You can use create_job in this way:

client = Client.create
job = client.create_job!(subject: 'Test', description: 'blabla')

When you declare a belongs_to association, the declaring class automatically gains five methods related to the association:

association
association=(associate)
build_association(attributes = {})
create_association(attributes = {})
create_association!(attributes = {})

In all of these methods, association is replaced with the symbol passed as the first argument to belongs_to.

more: http://guides.rubyonrails.org/association_basics.html#belongs-to-association-reference

回答5:

For creating new instances you could use factories. For this you could simply use FactoryGirl https://github.com/thoughtbot/factory_girl

So after you have defined your factory soewhat like this:

FactoryGirl.define do factory :job do client FactoryGirl.create(:client) subject 'Test' description 'This is a Test'

You could then call FactoryGirl.create(:job) to generate a new job like that. You could also call FactoryGirl.build(:job, client: aClientYouInstantiatedBefore, subject: 'AnotherTest') and also overwrite any other attributes

Factores are good if you want to create many objects, that are similar in a certain way.

来源：https://stackoverflow.com/questions/16286944/ruby-on-rails-creating-a-model-entry-with-a-belongs-to-association

标签

ruby-on-rails

ruby

ruby-on-rails-3

associations