####1. Name all the 7 (or 8) routes exposed by the resources keyword in the routes.rb file. Also name the 4 named routes, and how the request is routed to the controller/action.

For example by table posts:

Prefix Verb URI Controller#Action
posts GET /posts posts#index
new_post GET /posts/new post#new
POST /posts post#create
post GET /posts/:id post#show
edit_post GET /posts/:id post#edit
PUT/PATCH /posts/:id post#update
DELETE /posts/:id post#destroy

####2. What is REST and how does it relate to the resources routes?

REST is abbreviation for Representational State Transfer. It use a VERB and a URI to operate some action for web application. And it’s corespond to 4 HTTP VERB: GET, POST, PUT, DELETE with 7 actions: index, show, new, create, edit, update, destroy.

####3. What’s the major difference between model backed and non-model backed form helpers?

Model backed form from helpers like form_for, it can automatically association with objects in table, and it can dynamic generate coresponding element for different actions(ex. edit and new).

Non-model backed form from helpers like form_tag, it operate elements without relationship of tables in database.

####4. How does form_for know how to build the

element?

form_for based on given object, like this:

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<%= form_for @posts do |f| %>
  <%= f.label :title %>
  <%= f.text_field :title %>
  <%= f.submit %>
<% end %>

There’s a hidden attribute in form to record that what’s action for this request. Rails regconize this hidden attribute to build

element. It will automatically create submit button by what action is called.

####5. What’s the general pattern we use in the actions that handle submission of model-backed forms (ie, the create and update actions)?

For creating a post: POST /posts

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def create
  @post = Post.new(params.require(:post).permit!)
  if @post.save
    redirect_to posts_path
  else
    render :new
  end
end

For updating a post: PUT /posts/:id

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def update
  @post = Post.new(params.require(:post).permit!)
  if @post.save
    redirect_to post_path(@post)
  else
    render :edit
  end
end

####6. How exactly do Rails validations get triggered? Where are the errors saved? How do we show the validation messages on the user interface?

Rails validations get triggered in Model(ActiveRecord::Base), and errors are saved in Model.
We can use Model’s method to show error messages like this:

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instance.errors.full_messages

which instance is Model’s instance.

####7. What are Rails helpers?

Rails helpers is a way to implement DRY principle in View, it abstract redundant logic codes in Views into helpers.
This make code in View more cleaner without too much logic in it.

####8. What are Rails partials?

Rails partials is a way to implement DRY principle in View, it abstract redundant HTML codes in Views into partial forms.

####9. When do we use partials vs helpers?

Partials is to eliminate repeatedly HTML codes in Views, and helpers is to eliminate repeatedly logic codes in Views.

####10. When do we use non-model backed forms?

Some input or showing requirements do not need to be associated with tables in database.