I am having a question on scaffolding. Can someone explain what it does and how it works. I have search Google but I couldn't find anything that explained all the steps that happens.
A simple search in Google provides a lot of information. Also wikipedia
http://en.wikipedia.org/wiki/Scaffold_(programming)
Long story short a scaffold is simply a utility that most MVC web frameworks provide to create the necessary code/files for simple CRUD operations in the application.
In Rails, this means it will create the following from bottom up:
Active Record/Models
Migrations: These are used to create the necessary tables/columns for the model.
Models: Self explanatory, class of the model that subclasses from ActiveRecord::Base
Resource Routes
resources: :model: It generates the CRUD routes: index, show, new, create, edit, update, destroy by placing the resources: :model_name line in the routes.rb file.
ActionController
Controller: The controller that ties in the routes with the models and views with necessary code to perform the CRUD operations.
ActionView
Views: The views that display a very simplistic UI for performing the CRUD operations.
Assets: The javascripts, images, css, that are used in the views. This is very modular thanks to the assets pipeline.
It creates a bunch of other stuff based on your choices of test libraries. You can actually see what it's doing by just running rails scaffold SomeModel.
When I run the command:
rails generate scaffold peoples name:string age:integer
The following happens:
+ Rails connects to the database (defined in databases.yml) and creates a new table called peoples
+ In that table it creates two columns named name and age
+ Now it creates the web page that allows you to interface with the table
Scaffolding gives you a quick start on your Ruby on Rails projects.
Related
I am working on my first Rails app and I'm enjoying it so far. I am building my website on Bootstrap with SCSS. So until now, I didn't get to write any Ruby code, I've been just working on my views and generated 2 controllers until now.
I came at a situation where a controller should have more than one view. This is a products page... One action (ie. "show" action) should list all products, but when there is an ID present in the URL (ie. mysite.com/products/1) I want a different view to appear with the particular information of that view.
Well of course, I have no models or database data until now, no migrations no nothing, I am simply working on the design and later I'll work on the logic. However, I want to be able to differentiate views on mysite.com/products and mysite/products/N so I can work on my HTML/SCSS at least.
How can I achieve this? And how do I continue with my project's logic after I've set everything with the views?
At the command line:
$ rails new product_demo
$ cd product_demo
$ rails g controller Products
$ rails g model Product
Edit config/routes:
resources :products
Command line enter:
$ rake db:migrate
Edit `app/controllers/products_controller.rb:
def index
end
def show
end
Create app/views/products/index.html.erb:
Index page (put HTML here)
Create app/views/products/show.html.erb:
Detail page (put HTML here)
View the products index at:
http://localhost:3000/products/
View the product detail page (show view/action) at:
http://localhost:3000/products/1
No data yet, but that's okay and you can work on the general design. However if you want to work on the layout of the (eventual) data, you may want to start with a scaffold instead, the benefit of which is you can immediately begin entering data:
rails g scaffold Products name:string
The drawback of this approach is you'll have more stuff to remove to accomplish your design objectives, but you'll have a working app and can enter test data directly into the (generated) UI.
Now you can work on styling both pages, from your example: mysite.com/products (app/views/products/index.html.erb) and mysite.com/products/N (app/views/products/show.html.erb).
I'm learning RoR, and I'm getting very confused by the "_path" method as it's used in Controllers and Routes. To be more specific, I'm referring to the many different calls that take the syntax "(something)_path". So far as I know, they all seem to either encode or manipulate a URL or link. I'm having a hard time mastering the use of this type of method because I can't figure out what it's core functionality is supposed to be.
For example, I could use the following code to redirect an old URL structure to a page of listed Tweet instances in my config/routes.rb file:
get '/all' => 'tweets#index', as: 'all_tweets'
Only now can I use the following in an .erb file. Notice the "_path" code at the end of the line.
<%= link_to "All Tweets", all_tweets_path %>
I could also use the following code to create a link to an edit page (and another action) in a different .erb file:
<p><%= link_to tweet.user.name, edit_tweet_path(#tweet) %></p>
I've tried reading through my study materials as well as the RoR documentation, but I always end up more lost than when I began. Does anybody know the low-level definition of this "_path" method?
Helper
It's called a route helper, which means that Rails will generate them to help provide you with resource-based routing structures. I'll explain more in a second
--
To explain properly - Rails is just a framework.
Like all software, it is a series of files loaded in a particular order. As such, Rails creates a series of helper methods in the booting process. These "helper" methods can then be used throughout your application to call functionality / information as you require:
The Rails framework provides a large number of helpers for working
with assets, dates, forms, numbers and model objects, to name a few.
These helpers are available to all templates by default.
In addition to using the standard template helpers provided, creating
custom helpers to extract complicated logic or reusable functionality
is strongly encouraged. By default, each controller will include all
helpers. These helpers are only accessible on the controller through
.helpers
The route helpers (which are generated from your config/routes.rb file give you the ability to call routes which are resourceful. These might seem strange to begin with, but once you understand them, will help you inexorably.
--
Resourceful
To give you more clarity - Rails routes are known as resourceful
This means they are constructed around resources. To give you a brief definition of this, you need to appreciate that the resources of your application are the pools of data you can add to, and pull
from.
To explain further, because Rails is object orientated. If you're new, this won't mean very much, but keep it in mind, as when you progress through the language / work, you'll begin to see why this is important.
Object orientated programming puts OBJECTS at the center of the flow. Typically, you'd put logic at the center, but with OOP, it's the objects. This is very important for us, as it means that everything you do in Rails is based around the objects you can create.
As per the MVC principle (which, again, is what Rails is built on), you'll create / invoke your objects from your Models:
This means that if you want to create a series of routes to "CRUD" (Create Read Update Destroy) your objects, Rails is able to create the routes necessary to do that. This is where the resources directives come from inside the routes file:
Hope this helps!
Actually, these paths are generated based on your routes.rb. If you run this command at your project, you would be able to see all available on your app
rake routes
For example, if I declare my resources in routes.rb like this
resources :posts
then I would automatically have following available paths
posts_path
post_path
new_post_path
edit_post_path
If you use some strange abc_path which has not been declared in routes.rb, then you will get errors.
Hope this is helpful, you will definitely need to work more with Rails and then eventually you will understand all of these things :)
you could find definition for these methods in rails repository:
https://github.com/rails/rails/blob/master/actionpack/lib/action_dispatch/routing/route_set.rb#L127
I'm making a versioned JSON API in rails, where the controllers also respond to HTML, meaning it can be accessed as a browser or through an app I'm developing. The controllers have the form Model::V1::UsersController (Model instead of API since they don't just respond to JSON), and I currently have the following in my routes.rb:
namespace :model, path: 'm', as: '' do
# For objects in the model, accessible by JSON (through the app) or HTML (through the browser, using forms to send data to the server).
scope module: 'v1', constraints: OrConstraint.new([APIConstraint.new(1), APIConstraint.new(:default)]) do
resources :users do
collection do
post :sign_in
end
end
end
end
I plan to add more models to my API, but how can I use scaffolding to do this? For example, to create a controller Model::V1::CommentsController, but using the Comment model, instead of Model::V1::Comments.
I've been trying to figure this out for hours, and googling for people with similar problems shows that a few people say not to use scaffolding at all in this case: I don't want to do this, as it would mean writing all the views myself, which would be very time-consuming. Apart from that, I can't find much. nifty-generators was suggested somewhere, but it doesn't seem to be maintained anymore: no activity since 2012. I'm new to rails, and it might be that I've missed something quite obvious, but I find it surprising that not many others have had the same issue.
I've considered making my own generator, but looking at the source of https://github.com/rails/rails/blob/master/railties/lib/rails/generators/rails/scaffold/scaffold_generator.rb, it seems very complicated.
EDIT: I've just discovered that I can pass the --model-name parameter to the rails scaffold generator to achieve what I want, but for some reason it still tries to create a model with the same name as the controller. How can I change this?
I've settled with this solution, by not generating a model at all using the scaffold generator:
To create Model::V1::CommentsController as the controller and Comments as the model:
rails g model comment
rails g scaffold model/v1/comments --model-name=comment --no-orm
I created an object named settings. So i also provided its route in the routes.rb file i wrote "map.resources :settings". Now as i'm trying to save to the database with that object, it keeps on getting to the localhost:3000/settings url, which i don't have. i', also having this error
NameError in SettingsController#create
uninitialized constant SettingsController
PLEASE HELP! THANKS!
I am not 100% sure, but I believe you need to have a controller to add a route. Check out this diagram: http://ruby.railstutorial.org/ruby-on-rails-tutorial-book#sec:mvc
If you use Rails, you have to stick to its rules. Rails implements the MVC pattern, where the controller has the role to provide the linking between a request started in the client web page (view) to creating, reading, updating and deleting (CRUD) objects (== models). The routes.rb define here the mapping from the URL to controller actions, not directly to the resources. See the "Rails Guides for Routing" for more information.
If you want to use your model objects, Rails provides an easy way to start that: scaffolding. By using rails generate scaffold setting <attr_name1>:<type1> ..., you are able to create the following:
A migration for the database that creates the settings table.
Generation of the model object Setting that maps to the created database table.
A controller SettingsController that allows CRUD for your model objects.
View files for the actions generated for the controller.
You can all do that by hand, but it is a good starting point to begin with. And read the basic tutorials and play with the example applications to get a feeling for Rails ...
Hey, i have some experience with MVC. but I'm new to rails. I'm using the scaffold command to generate some default files. The model looks clean and nice, but the controller and the views aren't really dry. The contents of new.html.erb and edit.html.erb are almost the same and the methods new/edit and create/update are doing almost the same thing. In other frameworks i've used only one view for updating and creating new entries and also the same method in my controller by setting the id as an optional parameter. Do they use this structure to keep things RESTful (i have not much of a clue about rest :()? Is it the best practice to use this default stuff for crud?
The scaffold generator is a pretty good place to start. As you pointed out, there are some things which are not that great about it. I think most people take what the scaffold generates and then fix it up to their liking. For example, you can extract the form part from new.html.erb and edit.html.erb and place it in a partial _form.html.erb. Then update new.html.erb and edit.html.erb to include that partial to render the form. I think that for Rails 3, the scaffold generator has been changed to do this by default.
It does seem like new and edit, and create and update are pretty much the same, but you need to remember that they are mapped to different HTTP methods and URLs, which ties in to the whole RESTful resource idea. Check out the RailsGuides for routing, the section CRUD, Verbs, and Actions has a nice table of the seven different routes and the differences between them.
You should check out ryanb's nifty-generators:
http://github.com/ryanb/nifty-generators
The scaffolding creates a partial view called _form that then gets referenced from the new and edit views. It also comes with a bunch of other nice options -- like generating your views in haml or your tests in Shoulda or RSpec.
If they wanted you to keep it they wouldn't call it "scaffolding." It's just there to make everything work out of the box. If you put it into production you will more than likely be laughed at.