title: Rails: Multiple if conditions in validation
body: <p>Using: Rails 3.0.3</p>
  
  <p>I have validations such as this one:</p>
  
  <pre><code>  validates_numericality_of :person_weight_kg, :greater_than =&gt; 0, :message =&gt; "value_must_be_number_over_zero", :if =&gt; :bmi_calculation?, :if =&gt; :is_metric?   
  </code></pre>
  
  <p>That I would like to validate for multiple if-conditions (such as in the example). But it seems, however, that Rails treats these statements as OR. One returns false and one returns true which makes the validation go through.</p>
  
  <p>So, how do I check that this validation fulfills BOTH if-statements (bmi_calculation AND is_metric)?</p>