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POHow to access associated model through another model in Rails?
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copied!<p>UPDATE (specific and more detailed previous version is below):</p> <p>I'm developing a TV station web site. Here are requirements for my Program section:</p> <ol> <li>Each <code>Program</code> has ONE <code>Category</code>.</li> <li>Each <code>Program</code> has ONE <code>Subcategory</code>.</li> <li>Each <code>Category</code> has MANY <code>Subcategories</code></li> <li>Each <code>Category</code> has MANY <code>Programs</code>.</li> <li>Each <code>Subcategory</code> has ONE <code>Category</code></li> <li>Each <code>Subcategory</code> has MANY <code>Program</code>s.</li> </ol> <p>I want to retrieve all these three models to be associated. For example, I should be able to retrieve below data from my views:</p> <p>While:</p> <pre><code>p = Program.find(1) p_cat = ProgramCategory.find(1) p_subcat = ProgramSubcategory.find(1) </code></pre> <p>I should be able to retrieve and also EDIT these:</p> <pre><code>p.program_category p.program_subcategory </code></pre> <p>or</p> <pre><code>program_category.programs program_subcategory.programs </code></pre> <p>You can see what I tried below to achieve these requirements. You may recommend me a totally different way or fix my mistakes.</p> <p>Thank you</p> <p>============================================================</p> <p>I have 3 models. They are supposed to be nested in eachother.</p> <blockquote> <p>ProgramCategory > ProgramSubcategory > Program</p> </blockquote> <p>Here are my codes:</p> <p>ProgramCategory model:</p> <pre><code> has_many :programs has_many :program_subcategories </code></pre> <p>ProgramSubcategory model:</p> <pre><code>belongs_to :program_category has_many :programs </code></pre> <p>Program Model:</p> <pre><code>belongs_to :program_category belongs_to :program_subcategory </code></pre> <p>As I create a new Program, I can set its Category and everything is fine. I can access them from both sides. For example,</p> <pre><code>program.program_category </code></pre> <p>gives me what I expected. and also</p> <pre><code>program_category.programs </code></pre> <p>gives me what I want to have, too.</p> <p>BUT, -<em>here comes the question</em>-</p> <p>When I try to access <code>program.program_subcategory</code>, I receive just a nil.</p> <p>Eventhough my Subcategory's Category is set and my Program's Category is set too, why I can't access <code>program.program_subcategory</code> directly?</p> <p>When I type <code>program_category.program_subcategories</code>, I receive all Subcategories owned by that Category. But I CAN NOT get Subcategories from directly a <code>Program</code> object.</p> <p>My scheme is below. Any help is appriciated.</p> <pre><code>ActiveRecord::Schema.define(:version => 20120926181819) do create_table "program_categories", :force => true do |t| t.string "title" t.text "content" t.datetime "created_at", :null => false t.datetime "updated_at", :null => false end create_table "program_subcategories", :force => true do |t| t.integer "program_category_id" t.string "title" t.text "content" t.datetime "created_at", :null => false t.datetime "updated_at", :null => false end add_index "program_subcategories", ["program_category_id"], :name => "index_program_subcategories_on_program_category_id" create_table "programs", :force => true do |t| t.integer "program_category_id" t.integer "program_subcategory_id" t.string "title" t.text "content" t.datetime "created_at", :null => false t.datetime "updated_at", :null => false end add_index "programs", ["program_category_id", "program_subcategory_id"], :name => "my_join1", :unique => true end </code></pre>

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