Build a hash from an array

 We need to build a hash, and we need to build it from each element in an array.

Old way

  
def visitors_name_email
  result = {}
  visitors.each do |visitor|
    result[visitor.name] = visitor.email
  end
  result
end

New way

def visitors_name_email
  visitors.inject({}) do |result, visitor|
    result.merge(visitor.name => visitor.email)
  end
end