Plasticx Blog

Before coming to Ruby I had spent a lot of time coding Java and some C/C++ . Like any programmer I spend a lot of time working with data structures (and now blocks in Ruby). I would often fall back to idioms concerning data structure size in those legacy languages but in Ruby they are bad habits.

The Enumerable module that is mixed in to Array, Hash, and others is your friend. Use its idioms to tell you the state of your data structure rather raw details as in Java that imply state. For instance in Java, we test for elements in a collection with.size() (like myhash.size() == 0), but in Ruby having elements (or not) is more statefully conveyed with .any? and .empty?

Some goodies in Enumerable :

• any? – do we have any elements?
• empty? (in Array class) – are we void of elements?
• detect – return the first element that matches the criteria in the block
• select – return all the elements that match the criteria in a block
• each_with_index – enumerate over elements in the data structure AND automatically give me an index (which means I don’t have to predefine one)

And example in an irb session:

mike@butch 10001 ~$ irb
irb(main):001:0> a = ['hello', 'ruby-20', 'ruby']
=> ["hello", "ruby-20", "ruby"]
irb(main):002:0> a.detect{|v| v =~ /foo/}
=> nil
irb(main):003:0> a.detect{|v| v =~ /hello/}
=> "hello"
irb(main):004:0> a.detect{|v| v =~ /ruby/}
=> "ruby-20"
irb(main):005:0> a.select{|v| v =~ /ruby/}
=> ["ruby-20", "ruby"]
irb(main):006:0> a.empty?
=> false
irb(main):007:0> a.any?
=> true
irb(main):008:0> a.each_with_index{|v,i| puts "index: #{i}, val #{v}"}
index: 0, val hello
index: 1, val ruby-20
index: 2, val ruby
=> ["hello", "ruby-20", "ruby"]