Question

I’ve been using Java almost since it first came out but have over the last five years gotten burnt out with how complex it’s become to get even the simplest things done. I’m starting to learn Ruby at the recommendation of my psychiatrist, uh, I mean my coworkers (younger, cooler coworkers – they use Macs!). Anyway, one of the things they keep repeating is that Ruby is a ‘flexible’ language compared to older, more beaten-up languages like Java but I really have no idea what that means. Could someone explain what makes one language ‘more flexible’ than another? Please. I kind of get the point about dynamic typing and can see how that could be of benefit for conciseness. And the Ruby syntax is, well, beautiful. What else? Is dynamic typing the main reason?

Answer 1

Dynamic typing doesn’t come close to covering it. For one big example, Ruby makes metaprogramming easy in a lot of cases. In Java, metaprogramming is either painful or impossible.

For example, take Ruby’s normal way of declaring properties:

class SoftDrink   attr_accessor :name, :sugar_content end # Now we can do... can = SoftDrink.new can.name = 'Coke' # Not a direct ivar access — calls can.name=('Coke') can.sugar_content = 9001 # Ditto 

This isn’t some special language syntax — it’s a method on the Module class, and it’s easy to implement. Here’s a sample implementation of attr_accessor:

class Module   def attr_accessor(*symbols)     symbols.each do |symbol|       define_method(symbol) {instance_variable_get '@#{symbol}'}       define_method('#{symbol}=') {|val| instance_varible_set('@#{symbol}', val)}     end   end end 

This kind of functionality allows you a lot of, yes, flexibility in how you express your programs.

A lot of what seem like language features (and which would be language features in most languages) are just normal methods in Ruby. For another example, here we dynamically load dependencies whose names we store in an array:

dependencies = %w(yaml haml hpricot sinatra couchfoo) block_list %w(couchfoo) # Wait, we don't really want CouchDB! dependencies.each {|mod| require mod unless block_list.include? mod}