Ruby - How to skip/ignore specific lines when reading a file?

Question

What's the best approach for ignoring some lines when reading/parsing a file (using Ruby)?

I'm trying to parse just the Scenarios from a Cucumber .feature file and would like to skip lines that doesn't start with the words Scenario/Given/When/Then/And/But.

The code below works but it's ridiculous, so I'm looking for a smart solution :)

File.open(file).each_line do |line|
  line.chomp!
  next if line.empty? 
  next if line.include? "#"
  next if line.include? "Feature" 
  next if line.include? "In order" 
  next if line.include? "As a" 
  next if line.include? "I want"

You might want to look at using a custom Cucumber formatter: https://github.com/cucumber/cucumber/wiki/Custom-Formatters — Andy Waite, Apr 15 '13 at 18:03

score 6 · Accepted Answer · answered Apr 13 '13 at 21:47

6

You could do it like this:

a = ["#","Feature","In order","As a","I want"]   
File.open(file).each_line do |line|
  line.chomp!
  next if line.empty? || a.any? { |a| line =~ /#{a}/ }
end

answered Apr 13 '13 at 21:47

fmendez

7,250
5
36
35

steenslag · Answer 2 · 2013-04-13T23:23:42.067

5

The start_with? method accepts multiple arguments:

File.open(file).each_line do |line|
  next unless line.start_with? 'Scenario', 'Given', 'When', 'Then', 'And', 'But'
  # do something with line.
end

edited Apr 13 '13 at 23:23

answered Apr 13 '13 at 21:59

steenslag

79,051
16
138
171

@squiguy did I misunderstood this? "skip lines that doesn't start with the words Scenario/Given/When/Then/And/But." – steenslag Apr 14 '13 at 00:03
I guess he is contradicting himself then. Looks different from what is in his script. – squiguy Apr 14 '13 at 00:33
You're right steenslag: skip lines that doesn't start with the words Scenario/Given/When/Then. In the example I just shown the solution that I found to ignore the header of my .feature file. Anyway, thanks for your input. – user2253130 Apr 14 '13 at 16:57

score 1 · Answer 3 · answered Apr 14 '13 at 05:39

Use a Regular Expression for Compactness

You can replace most of your current loop with a single regular expression that uses alternation. You might also want to use String#chomp! as part of your conditional expression. For example:

File.open(file).each do |line|
  next if line.chomp! =~ /^$|#|Feature|In order|As a|I want/
  # something else
end

This reduces your block by six lines of code. Whether or not you find this alternative easier to read, it is certainly shorter and a bit more idiomatic. Your mileage may vary.

You might also find `next unless line.strip! =~ /^\s*(Scenario|Given|When|Then|And|But)/` a more reliable construct, but the expression in my original answer is closer to what you say already works for you. — Todd A. Jacobs, Apr 14 '13 at 05:53

score 0 · Answer 4 · answered Apr 13 '13 at 21:48

0

That's not that much help, but well, you might use array intersection for less code.

words = ["#", "Feature", "In order", "As a", "I want"]

File.open(file).each_line do |line|
  line.chomp!
  next if line.empty? || !(line.split & words).empty?

answered Apr 13 '13 at 21:48

konole

766
4
8

score 0 · Answer 5 · answered Apr 14 '13 at 05:00

Use the abstract method refctoring method! You could employ what ever technique ,clever or not-so-clever ,in the abstracted method.

File.open(file).each_line do |line|
         line.chomp!
         next if ignore(line)
end

def ignore line
#do whatever you like here, clever or straightforward. 
#All the techniques others has posted could be applied here
end

Ruby - How to skip/ignore specific lines when reading a file?

5 Answers5

Use a Regular Expression for Compactness