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    <p>Let's say <code>column_array[i] = "foo"</code>, for an example.</p> <p>If you want to call the <em>method</em> <code>r.foo</code>, use <code>Object#send</code>:</p> <pre><code> r.send(column_array[i], arg1, arg2, arg3, ...) </code></pre> <p>If you want to access <code>r</code>'s instance variable <code>@foo</code>, use <code>Object#instance_variable_get</code> and <code>Object#instance_variable_set</code>:</p> <pre><code> r.instance_variable_get('@'+column_array[i]) r.instance_variable_set('@'+column_array[i], new_value) </code></pre> <p>In this case we have to prepend the given name with an <code>@</code> sigil, since that is required at the start of all instance variable names.</p> <p>Since this is rails, and there's a whole lot of <code>ActiveRecord</code> magic going on with your models (and I'm guessing <code>Student</code> is a subclass of <code>ActiveRecord::Base</code>) you probably want to use the former, since <code>ActiveRecord</code> creates methods to access the database, and the values stored in instance variables may not be what you want or expect.</p> <p>I'll use an example from some test data I've got lying around:</p> <pre><code>% script/console Loading development environment (Rails 2.3.2) irb&gt; Customer #=&gt; Customer(id: integer, date_subscribed: datetime, rental_plan_id: integer, name: string, address: string, phone_number: string, credit_limit: decimal, last_bill_end_date: datetime, balance: decimal) irb&gt; example_customer = Customer.find(:all)[0] #=&gt; #&lt;Customer id: 6, date_subscribed: "2007-12-24 05:00:00", rental_plan_id: 3, name: "Evagation Governessy", address: "803 Asbestous St, Uneradicated Stannous MP 37441", phone_number: "(433) 462-3416", credit_limit: #&lt;BigDecimal:191edc0,'0.732E3',4(12)&gt;, last_bill_end_date: "2009-05-15 04:00:00", balance: #&lt;BigDecimal:191e870,'0.743E3',4(12)&gt;&gt; irb&gt; example_customer.name #=&gt; "Evagation Governessy" irb&gt; field = 'name' #=&gt; "name" irb&gt; example_customer.instance_variable_get(field) NameError: `name` is not allowed as an instance variable name from (irb):8:in `instance_variable_get` from (irb):8 irb&gt; example_customer.instance_variable_get('@'+field) #=&gt; nil irb&gt; example_customer.send(field) #=&gt; "Evagation Governessy" irb&gt; example_customer.send(field+'=', "Evagation Governessy Jr.") #=&gt; "Evagation Governessy Jr." irb&gt; example_customer.send(field) #=&gt; "Evagation Governessy Jr." irb&gt; example_customer.name #=&gt; "Evagation Governessy Jr." </code></pre> <p>So you can see how <code>#send(field)</code> accesses the record information, and trying to access the attributes doesn't. Also, we can use <code>#send(field+'=')</code> to change record information.</p>
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    1. COHi, yes Student is subclass of 'ActiveRecord::Base' class Student < ActiveRecord::Base thanks for your prompt reply, but the above does not work. Here's the situation, I have model named 'Student' That Student table in my database has columns named "student_identification", "laboratory_id", "email", "current_status" etc.. So I want to access them. The above are not methods or instance variables as you have specified. They are just columns names of the Student table. I hope I am clear to you. Please excuse the terms I am using to explain my code as i am completely new to rails. :)
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    2. COYou access the contents of columns through accessor methods in ActiveRecord. There is no concept of "just columns names" in Ruby.
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    3. COHi, Just to take make problem a little more advanced.. let's say your 'example_customer' object has a method called 'get_details_of_membership('membership_type')'. Here the 'membership_type' can be 'platinum', 'yearly', 'monthly' etc.. But if I used this command: example_customer.send('get_details_of_membership('platinum')') ,it won't work. actually I want to store the string 'get_details_of_membership('platinum')' in a variable like: field = 'get_details_of_membership('platinum')' and then do: example_customer.send(field) Can someone show me a way to tackle this one?
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