Pagination,Checking admin role and case statements in Ruby on Rails

a = User.where(:email => "chinna@yopmail.com").first
a.update_attributes(:age => 23)
(or)
a.age = 23
a.save
Collect the total user_ids
 user_ids = User.collect{|x|x.id}
 ######user_ids = [1,2,3,4,5,6] like that only you will get
 user_ids.each do |u|
 <%user = User.where(:id => u).first%>
<%=user.email%>
<%=user.name%>
 <%end%>

 ###pagination in rails with will_paginate gem
1)Controller
 @users= User.paginate(::page => params[:users], :per_page => 10)
2)in views
####<%= will_paginate @users, :param_name => 'users' %>
##display records in descending order
@user = User.order("created_at desc").limit(10)

###some of methods in model
  def check_admin?
    self.role == "admin"
  end

 ####In views <%if @user.check_admin? %>
<%=link_to "Users",users_path %>
 <%end%>

 ###case statements in ruby on rails
 def is_check_user(user)
   case user.role
   when "User"
   val = false
     when "Admin"
     val = true
   when "SuperAdmin"
     val =  true
     when "MarketingAdmin"
     val = false
     when "DataAdmin"
      val = true
     end
     return val
  end