Notes and code for 2015-02-19 open office hours session

Author: tannerwelsh

session-notes/2015-02-19/README.md

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+# Fundamentals of Web Development
+
+**February 19, 2015**
+
+Questions:
+
+- What are procs
+- Usage of instance variables, local variables, and symbols in Sinatra
+- Schema design in SQL & data modeling in Ruby
+- When to use helper functions in Sinatra
+- How much / what kind of code is conventionally allowed in views
+
+## Data Modeling / Schema Design
+
+Cities
+- name
+- population
+- elevation
+- mayor
+
+GasStations / PointsOfInterest
+- name
+- location (road)
+
+Roads
+- length
+- speed limit
+
+Route
+- start (city)
+- destination (city)
+- roads [sequence of ordered (roads)]
+
+
+```sql
+cities
+- id[key]
+- name[string]
+- population[int]
+- elevation[int]
+- mayor[string]
+
+gas_stations
+- id[int]
+- name[string]
+- road_id[foreign key]
+
+roads
+- id[int]
+- length[int]
+- speed_limit[int]
+
+route_sequence
+- id[key]
+- order[int]
+- route_id[foreign key -> routes]
+- road_id[foreign key -> roads]
+
+routes
+- id[int]
+- start_id[foreign key -> cities]
+- destination_id[foreign key -> cities]
+```
+
+```ruby
+class City
+  attr_accessor :name, :population, :elevation, :mayor
+end
+
+class PointOfInterest
+  # location is a Road instance
+  attr_accessor :name, :location
+end
+
+class Road
+  attr_accessor :length, :speed_limit
+end
+
+class Route
+  # start and destination are instances of City
+  # roads is an array of roads
+  attr_accessor :start, :destination, :roads
+end
+
+boston = City.new(name: "Boston")
+philly = City.new(name: "Philly")
+
+i95 = Road.new(length: 55, speed_limit: 65)
+i42 = Road.new(length: 45, speed_limit: 55)
+
+boston_to_philly = Route.new
+boston_to_philly.roads = [i42, i95]
+
+boston_to_philly.directions => "go on i42 for 45 miles then i95 for 55 miles"
+```
+
+```ruby
+# DataMapper implementation of the SQL schema
+
+class City
+  include DataMapper::Resource
+
+  property :name, String
+  property :population, Integer
+  property :elevation, Integer
+  property :mayor, String
+end
+
+class PointOfInterest
+  include DataMapper::Resource
+
+  property :name,
+  property :location
+end
+
+class Road
+  include DataMapper::Resource
+
+  property :length,
+  property :speed_limit
+
+  has n, :route_sequences
+  has n, :routes, through: :route_sequences
+end
+
+class RouteSequence
+  property :order, Integer
+
+  belongs_to :road
+  belongs_to :route
+end
+
+class Route
+  include DataMapper::Resource
+
+  belongs_to :start, ['City']
+  belongs_to :destination, ['City']
+
+  has n, :route_sequences
+  has n, :roads, through: :route_sequences
+end
+```

session-notes/2015-02-19/block-example.rb

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+class User
+  include DataMapper::Resource
+
+  get_time = lambda { DateTime.now }
+
+  self.created_at_config = GET_TIME
+  
+  @run_when_created = GET_TIME
+
+  before :create do
+    self.created_at = GET_TIME.call
+  end
+
+  def get_time
+    DateTime.now
+  end
+
+  property :created_at, DateTime
+end

session-notes/2015-02-19/helpers/app.rb

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+require 'sinatra'
+
+helpers do
+  def current_user
+    puts 'helper method'
+    @user ||= params[:user_id]
+  end
+end
+
+# def current_user
+#   puts 'global method'
+#   @user ||= params[:user_id]
+# end
+#
+# current_user
+
+get '/' do
+  # erb("<%= current_user %>")
+  # erb = "#{current_user}"
+  current_user
+end

session-notes/2015-02-19/lambda-example.rb

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+input_person = {
+  id: '213',                 # => "213"
+  name: 'buddy',             # => "buddy"
+  birthday: 'June 30, 1982'  # => "June 30, 1982"
+}                            # => {:id=>"213", :name=>"buddy", :birthday=>"June 30, 1982"}
+
+require 'date'  # => true
+
+class User
+  attr_accessor :id, :name, :birthday  # => nil
+
+  PARSER_FOR = {
+    id: lambda { |id| id.to_i },                   # => #<Proc:0x007fbba98fb788@/Users/tanner/Clients/codeunion/fundamentals-of-web-development/session-notes/2015-02-19/lambda-example.rb:13 (lambda)>
+    name: lambda { |name| name.capitalize },       # => #<Proc:0x007fbba98fb620@/Users/tanner/Clients/codeunion/fundamentals-of-web-development/session-notes/2015-02-19/lambda-example.rb:14 (lambda)>
+    birthday: lambda { |date| Date.parse(date) },  # => #<Proc:0x007fbba98fb530@/Users/tanner/Clients/codeunion/fundamentals-of-web-development/session-notes/2015-02-19/lambda-example.rb:15 (lambda)>
+  }                                                # => {:id=>#<Proc:0x007fbba98fb788@/Users/tanner/Clients/codeunion/fundamentals-of-web-development/session-notes/2015-02-19/lambda-example.rb:13 (lambda)>, :name=>#<Proc:0x007fbba98fb620@/Users/tanner/Clients/codeunion/fundamentals-of-web-development/session-notes/2015-02-19/lambda-example.rb:14 (lambda)>, :birthday=>#<Proc:0x007fbba98fb530@/Users/tanner/Clients/codeunion/fundamentals-of-web-development/session-notes/2015-02-19/lambda-example.rb:15 (lambda)>}
+
+  def self.from_hash(input_hash)
+    user = self.new               # => #<User:0x007fbba98fb030>
+
+    input_hash.each do |property, value|  # => {:id=>"213", :name=>"buddy", :birthday=>"June 30, 1982"}
+      PARSER_FOR[property].call(value)    # => 213, "Buddy", #<Date: 1982-06-30 ((2445151j,0s,0n),+0s,2299161j)>
+    end                                   # => {:id=>"213", :name=>"buddy", :birthday=>"June 30, 1982"}
+
+    user  # => #<User:0x007fbba98fb030>
+  end
+end
+
+User.from_hash(input_person)  # => #<User:0x007fbba98fb030>

session-notes/2015-02-19/sinatra-scope.rb

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+
+helpers do
+  def current_fruit
+    @fruit = 'bananas'
+  end
+
+  def double_age
+    age * 2
+  end
+end
+
+
+get '/' do
+  current_fruit # => bananas
+  @fruit = 'apple'
+  car = 'Buick'
+
+  erb(:home, locals: { age: 2 }) # => '<html>....'
+  erb :index # => '<html>....'
+  erb :save_user # => '<html>....'
+end
+
+# ----- home.erb
+
+# <%= @fruit %>
+# <%= car %>
+# <%= age %>