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    <p>short answer: it's impossible to store many values(all values in an array) into a column of a table.</p> <p>As you just want to store <code>subject_id</code>, I suppose you already have a table that stores all subjects and the only thing you want to do is setting a relationship between a specific user and the subjects he/she takes. A <code>many-to-many</code> relationship is the one you need.</p> <p>create a new table:</p> <pre><code>class CreateStuendship &lt; ActiveRecord::Migration def change create_table :stuedentships do |t| t.integer :subject_id t.integer :user_id # something else you want to store about this relationship, ex: year, semester... end end </code></pre> <p>app/models/studentship:</p> <pre><code>class Studentship &lt; ActiveRecord::Base belong_to :user belong_to :subject end </code></pre> <p>app/models/user.rb:</p> <pre><code>class User &lt; ActiveRecord::Base has_many :studentship has_many :subjects, :through =&gt; :studentship end </code></pre> <p>app/models/subject.rb:</p> <pre><code>class Subject &lt; ActiveRecord::Base has_many :studentship has_many :users, :through =&gt; :studentship end </code></pre> <p>furthermore, I think you can store your "period_no" and "day_no" into your <code>subjects</code> table, so you can know the time of the course by the subjects table. If the time of the course is not fixed( subjects with the same id have different course time), storing these two attributes into <code>studentship</code> may be a good idea. By doing so, you don't need the table <code>timetables</code>, which is unnecessary, anymore.</p> <p>when you want to store the subjects taken by a user, just create new studentships according to your array iteratively.</p> <p>Finally, you can </p> <pre><code>user = User.frist subject = Subject.first user.subjects # subjects taken by the first user subject.users # users who take the first subject </code></pre>
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    1. POhow do I save an array containing id values on ruby on rails
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    1. CO<% @subject_id.each do |ids| %> <%= text_field_tag 'gradeclassroomsubject_id[]', ids %> <% end %>
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    2. COThe relationship is between a classroom and subjects. example: Grade 9A can have multiple subjects. all this works fine the challenge here is to put this on the table that has the period no, subject and grade. so far with the code above I can store it on the array but when I click save I get this error message now "undefined method `stringify_keys' for"
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    3. COActually, you should mention this situation in your question.... here is the reason why you get this error: http://stackoverflow.com/a/1815730/938380 however, as I mentioned in the answer, it's impossible to store "many values" into "one column". I think replacing the `User` model I mentioned in the answer with your `Classroom` model is a much better idea. Also, it will be much easier to maintain in the future.
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