title: How does block argument work in ruby on rails?
body: <p>I am new to ruby and came across following snippet of code. class_a has a method, which takes some parameters and class_B.call method calls that method. 
  but on the method call there is => {|_a, array_value| array_value['value'] = '1234'} 
  after the method call, which i don't understand. when I hover over "_a" , it reads "unused block argument. 
  what is this construct => {|_a, array_value| array_value['value'] = '1234'} , which is after the method call. </p>
  
  <pre><code>class_A
    class &lt;&lt; self
      def method_A (count, *params) 
        #do soemthing
      end
    end
  end
  
   class_B
  
    def call
      class_A.Method_A(20) {|_a, array_value| array_value['value'] = '1234'}
    end
  
   end
  </code></pre>