Request denied while updating user details in rails - ruby-on-rails

Question

I'm new to ruby on rails.
I've two type of users Admin and User. Admin can create edit and destroy user. I've no problem with create and destroy and have implemented quite easily.
I've used following code in controller,
private
def allowed_params
params.require(:user).permit(:role_id, :email, :password, :password_confirmation, :fname, :lname)
end
to define parameters required and allowed while creating user.
User Create
def save_user
#user = User.new(allowed_params)
if #user.save
redirect_to list_users_path
else
render 'add_user'
end
end
User Update
def update_user
#user = User.find(params[:id])
if #user.update_attributes(allowed_params)
redirect_to list_users_path
else
render 'edit_user'
end
end
View
<div class="container">
<div class="row">
<div class="col-md-12">
<%= link_to "Admin Dashboard", admin_dashboard_path, :class=>'pull-left' %>
<%= form_for #user, :url => update_user_path do |f| %>
<div class="row">
<div class="col-md-12 field">
<div class="col-md-3">
<h2 style="text-align: center;">Edit User Details</h2>
</div>
</div>
</div>
<div class="row">
<div class="col-md-12 field">
<div class="col-md-3">
<%= f.label :fname, 'First Name' %><br />
<%= f.text_field :fname, :class => 'form-control' %>
<p class="error"><%= show_errors(#user, :fname) %></p>
</div>
</div>
</div>
<div class="row">
<div class="col-md-12 field">
<div class="col-md-3">
<%= f.label :lname, 'Last Name' %><br />
<%= f.text_field :lname, :class => 'form-control' %>
<p class="error"><%= show_errors(#user, :lname) %></p>
</div>
</div>
</div>
<div class="row">
<div class="col-md-12 field">
<div class="col-md-3">
<%= f.label :email, 'Email' %><br />
<%= f.text_field :email, :class => 'form-control' %>
<p class="error"><%= show_errors(#user, :email) %></p>
</div>
</div>
</div>
<div class="row">
<div class="col-md-12 field">
<div class="col-md-3" style="text-align: center">
<%= f.submit "Update User", :class => 'btn btn-sm btn-primary' %>
</div>
</div>
</div>
<% end %>
</div>
</div>
</div>
when I pass only fname, lname and email nothing happened. I need to update user details what should I do here ?
Any suggestion is appreciated.

Answer 1

There is a debug way.
You should launch the server in development mode. Then check the changes of development.log file in the terminal by tail -f log/development.log.
Then do what you want, such as click the "submit" button when you changed the fname or other fields.
Then focus on the informations got on step 1. There are what you can get:
A. which Controller and action handled the request
B. The parameters of this request.
C. The log of SQLs excuted by DB
D. The response status
Check if the right Controller? or right parameters? or SQLs has been excuted? In addition， we used to #user.update_attributes!(allowed_params) when debug. It take more informations when something disobeys the rules defined in Model(User).