How should I refactor this conditional code in ruby? - ruby

Question

How to refactor this function?
def split_description(first_n)
description_lines = description.split "\n"
line_num = description_lines.length
if line_num > first_n
#description_first = to_html(description_lines[0..first_n].join("\n"))
#description_remain = to_html(description_lines[first_n + 1..line_num].join("\n"))
elsif line_num > 1
#description_first = to_html(description_lines[0..first_n].join("\n"))
#description_remain = ''
else
#description_first = ''
#description_remain = ''
end
end
I am a Ruby starter and encounter this rubocup warning: Method has too many lines. [13/10]
The following is whole code url:
https://github.com/RubyStarts3/YPBT-app/blob/master/views_objects/video_info_view.rb

Answer 1

Code
def split_description(description, first_n)
#description_first, #description_remain =
case description.count("\n")
when 0..first_n
[description, '']
else
partition_description(description, first_n)
end.map(&:to_html)
end
def partition_description(description, first_n)
return ['', description] if first_n.zero?
offset = 0
description.each_line.with_index(1) do |s,i|
offset += s.size
return [description[0,offset], description[offset..-1]] if i == first_n
end
end
I've assumed to_html('') #=> '', but if that's not the case the modification is straightforward.
Example
So that we can see the effect of to_html, let's define it thusly.
def to_html(description)
description.upcase
end
description =<<_
It was the best of times
it was the worst of times
it was the age of wisdom
it was the age of fools
_
split_description(description, 0)
#description_first
#=> ""
#description_remain
#=> "IT WAS THE BEST OF TIMES\n..WORST OF TIMES\n..AGE OF WISDOM\n..AGE OF FOOLS\n"
split_description(description, 1)
#description_first
#=> "IT WAS THE BEST OF TIMES\n"
#description_remain
#=> "IT WAS THE WORST OF TIMES\n..AGE OF WISDOM\n..AGE OF FOOLS\n"
split_description(description, 2)
#description_first
#=> "IT WAS THE BEST OF TIMES\nIT WAS THE WORST OF TIMES\n"
#description_remain
#=> "IT WAS THE AGE OF WISDOM\nIT WAS THE AGE OF FOOLS\n"
split_description(description, 3)
#description_first
#=> "IT WAS THE BEST OF TIMES\n..WORST OF TIMES\n..AGE OF WISDOM\n"
#description_remain
#=> "IT WAS THE AGE OF FOOLS\n"
split_description(description, 4)
#description_first
#=> "IT WAS THE BEST OF TIMES\n..WORST OF TIMES\n..AGE OF WISDOM\n..AGE OF FOOLS\n"
#description_remain
#=> ""
Explanation
Firstly, is appears that description is a local variable holding a string. If so, it must be an argument of the method (along with first_n).
def split_description(description, first_n)
We want to assign values to two instance variables, so let's begin by writing
#description_first, #description_remain =
There are really two steps: obtaining the desired strings and then mapping them with to_html. So let's first concentrate on the first step.
We will now condition on the number of lines in the string
case description.count("\n")
First, let's deal with the case where the string contains no newlines
when 0
[description, '']
If the string is empty this will be ['', '']; otherwise it will contain a single string without a newline.
Next, suppose the number of newlines in the string is between 1 and first_n. In this case #description_first is to be the entire string and #description_remain is to be empty.
when 1..first_n
[description, '']
As both when 0 and when 1..first_n return the same two-element array, we can combine them:
when 0..first_n
[description, '']
To get this far, first_n is less than the number of newlines. I've used another method for the case where the number of newlines is greater than first_n.
else
partition_description(description, first_n)
partition_description simply determines the offset into description of the first_nth newline, and then partitions the string accordingly.
Lastly, we need to end the case statement, map the array of two strings returned with to_html and end the method
end.map(&:to_html)
end
As I mentioned earlier, I've assumed to_html('') #=> ''. That seems to me to be the best place do deal with empty strings.
Note that I've dealt with the string directly, rather than splitting the string into lines, manipulating the lines and then rejoining them.

Answer 2

Since it's used or blanked in every condition, initialize the instance variables to blank.
def split_description(first_n)
description_lines = description.split "\n"
line_num = description_lines.length
#description_first = ''
#description_remain = ''
if line_num > first_n
#description_first = to_html(description_lines[0..first_n].join("\n"))
#description_remain = to_html(description_lines[first_n + 1..line_num].join("\n"))
elsif line_num > 1
#description_first = to_html(description_lines[0..first_n].join("\n"))
end
end
I'd also move the logic for description_lines[first_n + 1..line_num].join("\n") to a method like to_html( whatever_that_is( lines, from, to) ) or the like. Then it's not so bad if you repeat the same call and the name will describe what it's doing.

Answer 3

If first_n is always greater than 1 I think you can modify a little the Schwern's answer:
...
#description_first = to_html(description_lines[0..first_n].join("\n")) if line_num > 1
if line_num > first_n
#description_remain = to_html(description_lines[first_n + 1..line_num].join("\n"))
end
end

Answer 4

This should work :
def split_description(description, first_n = 0)
lines = description.each_line
#description_first = to_html(lines.take(first_n).join)
#description_remain = to_html(lines.drop(first_n).join)
end
take and drop replace all your logic, because, as #Cary Swoveland mentionned in a comment :
if you take too much, you end up with the complete array, without error message
if you drop too much, you end ud with an empty array, without error message
Example :
[1,2].take(99) #=> [1, 2]
[1,2].drop(99) #=> []
Also each_line outputs an Array of Strings, with newlines still present. No split, chomp or join("\n") is needed.