Hash#deep_slice

gistfile1.rb

class Hash
  
  def deep_slice(*allowed_keys)
    sliced = { }
    allowed_keys.each do |allowed_key|
      if allowed_key.is_a?(Hash)
        key = allowed_key.keys.first
        sliced[key] = self[key].deep_slice(*[allowed_key.values].flatten) if self[key]
      else
        sliced[allowed_key] = self[allowed_key] if self[allowed_key]
      end
    end
    sliced
  end
  
end


class DeepSliceTest < Minitest::Test
  
  def test_deep_slice
    hash = {:a => 1, :b => {:c => 2, :d => {:e => 3, :f => 4}}, :g => 5}
    
    assert_equal hash, hash.deep_slice(:a, :b, :g)
    
    assert_equal ({:a => 1}), hash.deep_slice(:a)
    
    assert_equal ({:b => {:c => 2}}), hash.deep_slice(:b => :c)
    
    assert_equal ({
      :b => {:c => 2, :d => {:e => 3, :f => 4}},
    }), hash.deep_slice(:b => [:c, :d])
    
    assert_equal ({
      :b => {:c => 2, :d => {:e => 3}},
    }), hash.deep_slice(:b => [:c, :d => :e])
    
    assert_equal ({
      :b => {:d => {:e => 3}},
    }), hash.deep_slice(:b => {:d => :e})
    
    assert_equal ({}), hash.deep_slice(:x, :y, :z)
  end
  
end