Updated c4s3

Author: tomclose

_sessions/c4s2/3_setters.md

@@ -41,11 +41,12 @@ c.age #=> 7
 {% exercise %}
 Update your solution in `person.rb` to allow the `first_name` and `last_name` to be set independently, and have the `name` update accordingly:
 {%highlight ruby %}
-p = Person.new("Tom Close")
-p.name #=> "Tom Close"
+p = Person.new({:name => "Bart Simpson", :dob => "15/1/1990"})
 
-p.first_name = "Thomas"
-p.name #=> "Thomas Close"
+p.name #=> "Bart Simpson"
+
+p.first_name = "Bartholomew"
+p.name #=> "Bartholomew Simpson"
 {% endhighlight %}
 You might need to make changes to which attributes your class stores, to make this work.
 

_sessions/c4s2/5_homework.md

@@ -12,4 +12,74 @@ title: Homework
 We have only really begun to touch on what you can do with classes in ruby. There are really important concepts in object oriented programming (e.g. inheritance, class methods, class variables, mixins, etc.) that we haven't really mentioned at all. We'll meet some of these things in the next few weeks, but if you want a more comprehensive overview you can take a look at one of the following:
 
 - [http://phrogz.net/programmingruby/tut_classes.html](http://phrogz.net/programmingruby/tut_classes.html)
-- [http://juixe.com/techknow/index.php/2007/01/22/ruby-class-tutorial/](http://juixe.com/techknow/index.php/2007/01/22/ruby-class-tutorial/)
+- [http://juixe.com/techknow/index.php/2007/01/22/ruby-class-tutorial/](http://juixe.com/techknow/index.php/2007/01/22/ruby-class-tutorial/)
+
+## Getting set up with MongoDB
+
+Next session we will look at storing information in a database. The database we'll be using is [MongoDB](http://www.mongodb.org/).
+
+To use mongodb you need to have it running on your laptop. The database will run on one of your localhost ports (like sinatra), so that other processes can connect to it.
+
+The preparation falls into four parts:
+
+1. Install MongoDB.
+2. Start running the database.
+3. Install the gems to allow ruby to connect to MongoDB.
+4. Test your installation.
+
+We will look at these parts separately.
+
+### Install MongoDB
+
+If you installed `homebrew` ("The Hard Way", Mac only), your task is now easy. At the command line write:
+
+    brew install mongo
+
+If you didn't install homebrew (i.e. try doing the above and it doens't work), you will need to [download MongoDB](http://www.mongodb.org/downloads) from the site and follow the installation instructions for your system.
+
+{% exercise %}
+Install MongoDB either via
+
+    $ brew install mongo
+
+or by downloading and installing from the [MongoDB website](http://www.mongodb.org/downloads).
+{% endexercise %}
+
+### Start MongoDB running
+
+You can start MongoDB running from the command line:
+
+    $ mongod
+
+You will need to **keep this command line open** and open a new one to continue the instructions.
+
+By default mongo will run on [localhost:28017](http://localhost:28017/). If you visit that link in your browser you should see a mongo stats page.
+
+{% exercise %}
+1. Start MongoDB:
+
+        $ mongod
+
+2. Check the service is running at [localhost:28017](http://localhost:28017/).
+{% endexercise %}
+
+### Install the gems and test
+
+I've set up a project with the gems you need, so this should be straightforward:
+
+{% exercise %}
+1. Clone the project:
+
+        $ git clone https://github.com/code61/mongo_test.git
+
+2. Move into that folder and install the gems:
+
+        $ cd mongo_test
+        $ bundle install
+
+3. Test your installation:
+
+        $ ruby main.rb
+
+    If you see the text "Everything worked ok!", you're good to go!
+{% endexercise %}

_sessions/c4s3/1_intro_to_mongo.md

@@ -2,12 +2,6 @@
 title: About MongoDB
 ---
 
-{% exercise %}
-Clone the code for this session:
-
-        $ git clone https://github.com/code61/mongo1.git
-
-{% endexercise %}
 
 In this session we will be using a database - a specialised piece of software for storing and retrieving data. Databases become important when you have large amounts of data, which you want to be able to access quickly and which you want to keep consistent.
 
@@ -20,6 +14,69 @@ MongoDB is one of many different databases that we could have chosen. We went wi
 
 MongoDB is a *NOSQL*, or *document-based*, database. In the past, the more traditional style *SQL*, or *relational*, databases were used in most applications. NOSQL databases have risen in popularity in the last year or two, in part due to their ability to offer increased performance in certain common scenarios, by allowing developers to bend the rigid SQL database structures. We will go into this in slightly more depth later in the course. For the time being, with data we're storing in the next few sessions it won't make much difference whether our db is SQL or NOSQL.
 
+### Using Mongoid
+
+Mongoid is a ruby library that allows you to interface with MongoDB. The idea is very simple - you can think of Mongoid as mapping **classes** in your application to **tables** in the database. Take a look at the following example:
+
+{% highlight ruby %}
+class Athlete
+  include Mongoid::Document
+
+  field :name,    type: String
+  field :country, type: String
+  field :age,     type: Integer
+  field :height,  type: Integer
+  field :weight,  type: Integer
+  field :sex,     type: String
+  field :dob,     type: Time
+  field :gold,    type: Integer
+  field :silver,  type: Integer
+  field :bronze,  type: Integer
+  field :sport,   type: Integer
+  field :events,  type: Array
+
+  def total_medals
+    bronze + silver + bronze
+  end
+end
+{% endhighlight %}
+
+This is fairly similar to the classes we looked at last week - we have data and methods that act on the data. The two different parts are:
+
+* `include Mongoid::Document`: this activates this class as a mongoid-enabled class.
+* The `field :name, type: String` etc.: these setup the getting and setting methods that we had to do by hand last week, and tell mongoid what sort of object it is, which is useful for storage purposes.
+
+You can use this class like this:
+{% highlight ruby %}
+a = Athlete.new
+a.name    = "Michael Phelps"
+a.country = "US"
+a.sport   = "Swimming"
+a.gold    = 2
+a.silver  = 2
+a.bronze  = 0
+
+a.name         #=> "Michael Phelps"
+a.total_medals #=> 4
+{% endhighlight %}
+
+This is not that exciting - we could have done all this last week. It gets more interesting when we start using some of the extra methods that Mongoid has added to the `Athlete` class:
+
+{% highlight ruby %}
+# Let's save Michael in the database
+a.save    #=> true
+
+# How many athletes do we have?
+Athlete.count  #=> 1
+
+# Let's pull Michael out again
+a = Athlete.first #=> #<Athlete _id: 5315dec6de9c928a02001c9c, name: "Michael Phelps", country: "US", gold: 2, silver: 2, bronze: 0, sport: "Swimming">
+
+# or
+a = Athlete.find_by(:name => "Michael Phelps") #=> #<Athlete _id: 5315dec6de9c928a02001c9c, name: "Michael Phelps", country: "US", gold: 2, silver: 2, bronze: 0, sport: "Swimming">
+
+{% endhighlight %}
+
 
 ### Starting MongoDB
 
@@ -31,35 +88,47 @@ You will need to keep this command line open and continue the instructions in a
 
 By default mongo will run on [localhost:28017](http://localhost:28017/). If you visit that link in your browser you should see a mongo stats page.
 
-### Using it in ruby
+{% exercise %}
+1. Start MongoDB running on your laptop.
+1. Clone down the code for the session: [https://github.com/code61/sinatra_c4s3](https://github.com/code61/sinatra_c4s3)
+2. Run `bundle install` to get the required gems.
+3. Open up `irb`.
+4. Type `require './utils'` (this loads in the `Athlete` class and sets up your MongoDB connection).
+5. Try the following
+{% highlight ruby %}
+a = Athlete.new
+a.name    = "Michael Phelps"
+a.country = "US"
+a.sport   = "Swimming"
+a.gold    = 2
+a.silver  = 2
+a.bronze  = 0
 
-To interface with MongoDB from ruby we will be using the [Mongoid](http://mongoid.org/) gem. You should have installed the gem already, but if not,
+a.name
+a.country
 
-    $ gem install mongoid
+a.save
 
-should do the trick.
+Athlete.count
+b = Athlete.first
 
-We then need to set some configuration options in our ruby project. Among other things this tells the project which of the mongodb databases on your computer to use - usually you'd want each project to have its own database. The following configuration options should go in a `mongoid.yml` file:
+b.name
+b.name = "Tom Close"
 
-{% highlight yaml %}
-development:
-  sessions:
-    default:
-      hosts:
-        - localhost:27017
-      database: mongo_examples
-  options:
-    raise_not_found_error: false
-{% endhighlight %}
+a.name     # has this updated?
 
-You then need to include the following code in your `app.rb` (or similar) file:
+b.save
+a.name     # has it updated now?
 
-{% highlight ruby %}
-require 'mongoid'
-require 'json'
+a.reload
+a.name
 
-Mongoid.load!("mongoid.yml", :development)
-{% endhighlight %}
-
-We've seen the `require` statements before - they just tell ruby that we'd like to use the `mongoid` library (and also `json`). The line `Mongoid.load!("mongoid.yml", :development)` tells `mongoid` where to find the configuration options. The `:development` bit refers to our environment - you will probably want to have different configuration options when you're deploying your app to heroku; mongoid allows this by specifying `:production` and `:development` environments.
+# different way of creating an athlete, using a hash
+c = Athlete.new(:name   => "Chad Le Clos", :country => "South Africa", 
+                :sport  => "Swimming",     :gold    => 1,
+                :silver => 1,              :bronze  => 0 )
+c.save
 
+d = Athlete.find_by(:name => "Chad Le Clos")
+{% endhighlight %}
+{% endexercise %}

_sessions/c4s3/2_mongo_classes.md

@@ -0,0 +1,69 @@
+---
+title: Searching and sorting
+---
+
+One thing that databases are good at is searching for records. Mongoid allows you to search for records in various different ways: 
+
+{% highlight ruby %}
+Athlete.find_by(:name => "Michael Phelps")
+
+Athlete.find_by(:gold => 2)   # returns the first one it finds
+
+Athlete.where(:gold => 2)     # returns a 'collection' with all of them
+
+# you can do lots of things with collections e.g. counting
+Athlete.where(:gold => 2).count
+# or iterating
+Athlete.where(:gold => 2).each do |a|
+  puts a.name
+end
+# or summing
+Athlete.where(:gold => 2).sum(:age)
+# or turn it into an array
+Athlete.where(:gold => 2).to_a
+
+# searching on multiple things at once
+Athlete.where(:gold => 2, :bronze => 3)
+# or
+Athlete.where(:gold => 2).where(:bronze => 0)
+
+# searching on conditions
+Athlete.where(:gold.gte => 2)
+
+{% endhighlight %}
+
+You can find further examples in the [Mongoid docs](http://mongoid.org/en/mongoid/docs/querying.html#queries).
+
+### Sorting
+
+You can also get the database to return things to you sorted:
+
+{% highlight ruby %}
+
+# these both return collections
+Athlete.order_by(:age.asc)
+Athlete.order_by(:age.desc)
+
+# you can then do things like
+# .. take the first 1
+Athlete.order_by(:age.asc).first
+
+# .. or the first 10
+Athlete.order_by(:age.asc).limit(10).to_a
+
+{% endhighlight %}
+
+
+{% exercise %}
+1. Open `irb` and do `require './utils'`.
+2. Call the function `load_athletes`. This loads in all the athletes from London 2012.
+3. Answer the following questions:
+    1. How many athletes were there?
+    2. How many women? How many men?
+    3. Who was the oldest athlete?
+    4. Who was the youngest?
+    4. How many people won at least 1 gold?
+    5. What was the average age? (Your answer should have decimal places..)
+    6. Who got the most golds?
+    7. Who was the 10th oldest athlete?
+{% endexercise %}