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"

Answer 1

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

Answer 2

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

Answer 3

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.

Answer 4

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?

Answer 5

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