CODEWITHSUNDEEP
ruby-on-railsforms
Iggy
Iggy

Reputation: 5251

What happens to @user in new and create?

I was reading this article about new, create, and forms and there are a few parts on User creation process that I don't fully understand.

I want to create User with basic attributes: name, email. On routes I have resources :user, and:

users_controller.rb

def new
    @user = User.new
end

def create
    @user = User.new(params[:user])
    if @user.save
        redirect_to @user, alert: "User created successfully."
    else
        redirect_to new_user_path, alert: "Error creating user."
    end
end


views/users/new.html.erb

<%= form_for(@user) do |f| %>
    <%= f.label :name %>
    <%= f.text_field :name %>

    <%= f.label :email %>
    <%= f.text_field :email %>
    ...

on new instance variable @user is created: @user = User.new. Now, I understand that this new @user is the same @user used in <%= form_for(@user) do |f| %>(right?). I don't understand when @user in create method comes in.

There is no create.html.erb because create is really a POST request. Does that mean @user on create gets passed on from new's @user? When does create method gets activated? Why do I need to declare @user = User.new in both new and create? When does create's @user gets saved (in other word, what action saves this new user instance)?

I apologize for the many questions. There are a lot of behind-the-scenes that I don't know. If I have to sum it up, what I want to understand is:

How does form_for work with new and create to create user and what does form_for do with each new's@user and create's @user?

Upvotes: 0

Views: 44

Answers (2)

Frederick Cheung
Frederick Cheung

Reputation: 84142

Rails copies controller instance variables to whatever view is rendered: when the new view is rendered, the @user variable has the same value as @user in the controller.

The create method is called when the form is submitted (when the user clicks submit). It creates a new instance of User, using the submitted parameters. Every http request is processed by a new instance of the appropriate controller, so this @user is unrelated to the instance from the new action. Nothing happens in terms of the database until the call to @user.save

Upvotes: 0

Cjmarkham
Cjmarkham

Reputation: 9700

You are correct. when you POST to the user route, it re-renders the new method, unless you redirect or render another method. So declaring the instance variable @user in the create method allows this to be passed back to the new template. If you didn't specify this instance variable, Rails would complain that the form param can't be blank since @user isn't set (Since the method rendering the template is create not new).

Upvotes: 1

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