Merge pull request #198 from trishume/master

Explain Blocks In Ruby

ruby.html.markdown

@@ -5,6 +5,7 @@ contributors:
   - ["David Underwood", "http://theflyingdeveloper.com"]
   - ["Joel Walden", "http://joelwalden.net"]
   - ["Luke Holder", "http://twitter.com/lukeholder"]
+  - ["Tristan Hume", "http://thume.ca/"]
 ---
 
 ```ruby
@@ -158,11 +159,6 @@ hash['number'] #=> 5
 # Asking a hash for a key that doesn't exist returns nil:
 hash['nothing here'] #=> nil
 
-# Iterate over hashes with the #each method:
-hash.each do |k, v|
-  puts "#{k} is #{v}"
-end
-
 # Since Ruby 1.9, there's a special syntax when using symbols as keys:
 
 new_hash = { defcon: 3, action: true}
@@ -191,9 +187,14 @@ end
 #=> iteration 4
 #=> iteration 5
 
-# HOWEVER
-# No-one uses for loops
-# Use `each` instead, like this:
+# HOWEVER, No-one uses for loops.
+# Instead you should use the "each" method and pass it a block.
+# A block is a bunch of code that you can pass to a method like "each".
+# It is analogous to lambdas, anonymous functions or closures in other programming languages.
+#
+# The "each" method of a range runs the block once for each element of the range.
+# The block is passed a counter as a parameter.
+# Calling the "each" method with a block looks like this:
 
 (1..5).each do |counter|
   puts "iteration #{counter}"
@@ -204,6 +205,17 @@ end
 #=> iteration 4
 #=> iteration 5
 
+# You can also surround blocks in curly brackets:
+(1..5).each {|counter| puts "iteration #{counter}"}
+
+# The contents of data structures can also be iterated using each.
+array.each do |element|
+  puts "#{element} is part of the array"
+end
+hash.each do |key, value|
+  puts "#{key} is #{value}"
+end
+
 counter = 1
 while counter <= 5 do
   puts "iteration #{counter}"