understanding of rails object life cycle issue - ruby-on-rails

Question

I am new to rails.I have some confusion about about rails object life cycle.In rails we have the bellow code.
class UsersController < ApplicationController
# GET /users
# GET /users.json
def index
#users = User.all
respond_to do |format|
format.html # index.html.erb
format.json { render json: #users }
end
end
# GET /users/1
# GET /users/1.json
def show
#user = User.find(params[:id])
respond_to do |format|
format.html # show.html.erb
format.json { render json: #user }
end
end
# GET /users/new
# GET /users/new.json
def new
#user = User.new
respond_to do |format|
format.html # new.html.erb
format.json { render json: #user }
end
end
# GET /users/1/edit
def edit
#user = User.find(params[:id])
end
# POST /users
# POST /users.json
def create
#user = User.new(params[:user])
respond_to do |format|
if #user.save
format.html { redirect_to #user, notice: 'User was successfully created.' }
format.json { render json: #user, status: :created, location: #user }
else
format.html { render action: "new" }
format.json { render json: #user.errors, status: :unprocessable_entity }
end
end
end
# PUT /users/1
# PUT /users/1.json
def update
#user = User.find(params[:id])
respond_to do |format|
if #user.update_attributes(params[:user])
format.html { redirect_to #user, notice: 'User was successfully updated.' }
format.json { head :no_content }
else
format.html { render action: "edit" }
format.json { render json: #user.errors, status: :unprocessable_entity }
end
end
end
# DELETE /users/1
# DELETE /users/1.json
def destroy
#user = User.find(params[:id])
#user.destroy
respond_to do |format|
format.html { redirect_to users_url }
format.json { head :no_content }
end
end
end
then in the form we have
<%= form_for(#user) do |f| %>
<% if #user.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#user.errors.count, "error") %> prohibited this user from being saved:</h2>
<ul>
<% #user.errors.full_messages.each do |msg| %>
<li><%= msg %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field">
<%= f.label :name %><br />
<%= f.text_field :name %>
</div>
<div class="field">
<%= f.label :email %><br />
<%= f.text_field :email %>
</div>
<div class="actions">
<%= f.submit %>
</div>
<% end %>
my confusion is in the new action in controller i have #user = User.new
and again in the create #user = User.new(params[:user]).
then in form i have <%= form_for(#user) do |f| %> .
My question is here at the form the #user object actually means waht?
I mean does this #user is going to hit the new action or create action.
If it is going to hit the create action then how this is happening because the form is actually comes from the new action so i can't figure it out how its hitting to the create action .
i know its very simple question.But i dont know how its happening as i am new to rails.
Please help me to make me understand the object flow.
thanks in advance.

Answer 1

The "new" action makes a new object and shows a form for editing it. That form submits to the "create" action because the object has not been saved yet.
If you did
form_for #user
and #user was a previously-saved object, the form would submit to the update action instead.
form_for is a bit magical, like a lot of rails: it does two things:
sets the "action" attribute of the form to point at either "/users" (for create) and "/users/:id" (for update)
in the case of update (ie for objects that already have an id) it also adds a hidden field which triggers the update action: this hidden field will look like this: <input type="hidden" value="put" name="_method">.
Have a look at form_for in your rails api.

Answer 2

It's hitting create action because of the proper form URL. When you run rake routes command, you'll see that POST /users leads to users#create action - and that's the URL in the new form. URL is set (and form fields are generated) properly by Rails because you pass User instance to the form.