how to pass a value to check_box in Rails4

Question

I am using rails 4 and ruby 2. I want to pass a value in the check_box. If I checked it, then it should take value =3 else "select_MedicalCenter" will be displayed and :medical_center_id can be selected from there. I did this and its not working.

<div id ="display_box" >
<%= f.label :assoiated_to_none %>
<%= f.check_box :medical_center_id, { checked: true },'3',:onchange=>"$('#select_MedicalCenter').show();"%>
</div>
<div id="select_MedicalCenter" style="display:none;"><%= f.label :medical_center %><br />
<%= f.collection_select :medical_center_id,MedicalCenter.all,:id,:name,:prompt=>true%>
</div>

Answer 1

I found the answer. I added a javascript code.

$("input:checkbox[name='user[medical_center_id]']").change(function(){  
           if(this.checked){
             this.value=3;
            }
});