Flattening hash into string in Ruby

Question

Is there a way to flatten a hash into a string, with optional delimiters between keys and values, and key/value pairs?

For example, print {:a => :b, :c => :d}.flatten('=','&') should print a=b&c=d

I wrote some code to do this, but I was wondering if there was a neater way:

class Hash   def flatten(keyvaldelimiter, entrydelimiter)     string = ""     self.each do       |key, value|       key = "#{entrydelimiter}#{key}" if string != "" #nasty hack       string += "#{key}#{keyvaldelimiter}#{value}"       end     return string   end end  print {:a => :b, :c => :d}.flatten('=','&') #=> 'c=d&a=b' 

Thanks

Answer 1

I wouldn't override .flatten, which is already defined:

Returns a new array that is a one-dimensional flattening of this hash. That is, for every key or value that is an array, extract its elements into the new array. Unlike Array#flatten, this method does not flatten recursively by default. If the optional level argument determines the level of recursion to flatten.

This is simplest way to do it that I'm aware of:

{:a => 100, :b => 200}.map{|k,v| "#{k}=#{v}"}.join('&') # => "a=100&b=200"

Answer 2

Slight variation of @elektronaut's version:

You can actually put just an |e| there instead of |k, v| in which case e is an array of two elements and you can call e.join('='). Altogether you have something like

class Hash   def join(keyvaldelim=$,, entrydelim=$,) # $, is the global default delimiter     map {|e| e.join(keyvaldelim) }.join(entrydelim)   end end  {a: 100, b: 200}.join('=', '&') # I love showing off the new Ruby 1.9 Hash syntax # => 'a=100&b=200'