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POHow can I access an ActiveRecord grandparent association through a parent association that has not yet been saved?
 

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  1. POHow can I access an ActiveRecord grandparent association through a parent association that has not yet been saved?
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    <p>I have a situation where I would like access to an associated grandparent before the parent object is saved. I can think of several hacks, but I'm searching for a clean way to accomplish this. Take the following code as an illustration of my problem:</p> <pre><code>class Company &lt; ActiveRecord::Base has_many :departments has_many :custom_fields has_many :employees, :through =&gt; :departments end class Department &lt; ActiveRecord::Base belongs_to :company has_many :employees end class Employee &lt; ActiveRecord::Base belongs_to :department delegate :company, :to =&gt; :department end company = Company.find(1) # =&gt; &lt;Company id: 1&gt; dept = company.departments.build # =&gt; &lt;Department id: nil, company_id: 1&gt; empl = dept.employees.build # =&gt; &lt;Employee id: nil, department_id: nil&gt; empl.company # =&gt; Employee#company delegated to department.company, but department is nil </code></pre> <p>I'm using Rails 3.2.15. I understand what is happening here, and I understand why empl.department_id is nil; though I wish Rails held a direct reference to the prospective association prior to calling save, such that the last line could be delegated through the unsaved department object. Is there a clean work around?</p> <p>UPDATE: I've tried this in Rails 4 as well, here is a console session:</p> <pre><code>2.0.0-p247 :001 &gt; company = Company.find(1) Company Load (1.5ms) SELECT "companies".* FROM "companies" WHERE "companies"."id" = ? LIMIT 1 [["id", 1]] =&gt; #&lt;Company id: 1, name: nil, created_at: "2013-10-24 03:36:11", updated_at: "2013-10-24 03:36:11"&gt; 2.0.0-p247 :002 &gt; dept = company.departments.build =&gt; #&lt;Department id: nil, name: nil, company_id: 1, created_at: nil, updated_at: nil&gt; 2.0.0-p247 :003 &gt; empl = dept.employees.build =&gt; #&lt;Employee id: nil, name: nil, department_id: nil, created_at: nil, updated_at: nil&gt; 2.0.0-p247 :004 &gt; empl.company RuntimeError: Employee#company delegated to department.company, but department is nil: #&lt;Employee id: nil, name: nil, department_id: nil, created_at: nil, updated_at: nil&gt; 2.0.0-p247 :005 &gt; empl.department =&gt; nil </code></pre> <p>UPDATE 2: Here is a <a href="https://github.com/dissolved/activerecord_deep_obj_linking" rel="nofollow">test project on github</a>.</p>
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    1. USRyan Sandridge
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    1. COHow very weird. I must try it out again later. It worked cheerfully enough last night. Check if `empl.association(:department) == Employee.new.association(:department)`...
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      1. POHow can I access an ActiveRecord grandparent association through a parent association that has not yet been saved?
      1. USstruthersneil
    2. COThe result of that expression is `false`. I see there is an instance variable `@target` on the association, which always seems to be `nil` (even for saved records). I don't know what `@target` is suppose to be, but it would make sense to me that it would contain the reference I'm desiring.
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      1. USRyan Sandridge
 

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