```ruby
# Longest String

# I worked on this challenge by myself.

# longest_string is a method that takes an array of strings as its input
# and returns the longest string
#
# +list_of_words+ is an array of strings
# longest_string(list_of_words) should return the longest string in +list_of_words+
#
# If +list_of_words+ is empty the method should return nil


# Your Solution Below
def longest_string(list_of_words)
  list_of_words.sort_by { |string| string.length }
  return list_of_words[-1]
end```

Complete solution and spec files for longest string
user
```ruby
# Longest String

# I worked on this challenge by myself.

# longest_string is a method that takes an array of strings as its input
# and returns the longest string
#
# +list_of_words+ is an array of strings
# longest_string(list_of_words) should return the longest string in +list_of_words+
#
# If +list_of_words+ is empty the method should return nil


# Your Solution Below
def longest_string(list_of_words)
  list_of_words.max_by { |string| string.length}
end```
assistant