hash_accessor.rb

module HashAccessor
  def method_missing(name, *args, &block)
    h = Hash[self.map{|(k,v)| [k.to_sym,v]}]

    if h.has_key?(name.to_sym)
      h[name.to_sym]
    end
  end
end

hash_accessor_spec.rb

describe HashAccessor do
  class Hash
    include HashAccessor
  end

  context "hash symbol keys" do
    subject { {a: 1, b: 2} }
    its(:a) { should == 1 }
    its(:b) { should == 2 }
    its(:c) { should be_nil }
    its('a') { should == 1 }
    its('b') { should == 2 }
    its('c') { should be_nil }
  end

  context "hash string keys" do
    subject { {'a' => 1, 'b' => 2} }
    its(:a) { should == 1 }
    its(:b) { should == 2 }
    its(:c) { should be_nil }
    its('a') { should == 1 }
    its('b') { should == 2 }
    its('c') { should be_nil }
  end

  context "empty hash" do
    subject { {} }
    its(:a) { should be_nil }
  end
end