**View concepts we will cover: **
local variables for repeating elements
This was a question from @photonerddan during class, and after looking through many examples online approaching it from an inheritance stance, as well as ones with examples that seemed outside of common use-cases, Mike and I decided to approach it from a problem / solution standpoint, which looks at it from a database perspective.
We will cover it more in-depth during the second week of Rails MakerSquare, but for now here is a short example to highlight the problem that polymorphism is solving in your database.
So let's start with the problem it is solving:
Polymorphism keeps you from having excessive foreign key columns in a database table where multiple things, such as notification feed items, are owned by other objects.
| require 'digest/md5' | |
| # make an email array for images you want to find | |
| array_emails = ["email1", ...] | |
| # make a new hash to store email:image_url as a key value pair | |
| hash_email_image = {} | |
| def gravatar_for(email, options = { size: 50 }) | |
| gravatar_id = Digest::MD5::hexdigest(email.downcase) | |
| size = options[:size] | |
| gravatar_url = "https://secure.gravatar.com/avatar/#{gravatar_id}?s=#{size}" |
Up until now we have looked at the create and update controller action in Rails in the context of using a basic <html> form tag, <form></form>.
When you wanted to POST a new movie to your Metube app:
First you made a new controller-action in your videos controller. This action was mapped to the GET route that loaded the new video form from the views/videos/new.html.erb file with a route that looks like get "/videos/new", to: "videos#new" in the routes.rb file.
Looking at the new action in the videos controller, it's time to come clean. There was really no reason in the previous Rails CRUD lesson with the new action that we needed to hand down this instance variable:
| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <style> | |
| body {margin: 0;} | |
| .container { | |
| margin: 0 auto; | |
| width: 800px; | |
| background: aliceblue; | |
| } |
| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="utf-8"> | |
| <meta http-equiv="X-UA-Compatible" content="IE=edge"> | |
| <title>Shoestring.css Style Guide</title> | |
| <meta name="description" content=""> | |
| <meta name="viewport" content="width=device-width, initial-scale=1"> | |
| <link rel="stylesheet" href="./css/shoestring/0.0.1/shoestring-dev.css"> | |
| <style type="text/css"> |
| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="utf-8"> | |
| <meta http-equiv="X-UA-Compatible" content="IE=edge"> | |
| <title>Clearfix Example</title> | |
| <meta name="description" content=""> | |
| <meta name="viewport" content="width=device-width, initial-scale=1"> | |
| <style type="text/css"> | |
| /* code for debugging */ |
| (function(){ | |
| var marginSetter = function () { | |
| var h = ($(window).height()) / .2; | |
| $('#my-element').css("margin-top": h); | |
| }; | |
| // to run when the window is resized | |
| $(window).on('resize', function() { | |
| marginSetter(); |
| <div id="result">result text</div> | |
| (function(){ | |
| var resizeText = function() { | |
| var text = $("#result").html(); | |
| var length = text.length; | |
| if (length > 30){ | |
| $("#result").css("font-size", "0.7em"); | |
| } |
| # Create our module. This is so other files can start using it immediately | |
| module RPS | |
| end | |
| # Require all of our project files | |
| # require_relative 'rps/player.rb' | |
| # require_relative 'rps/match.rb' | |
| # require_relative 'rps/round.rb' |