Ruby：使用正则表达式的.grep

Question

I'm using a regular expression to replace all '*' with '[A-Za-z0-9]*' except when the '*' is preceded by '\\' like '\\*' . How can I ignore the case '\\*' ?

code:

puts Regexp.new(val.gsub(/^\*/,'[A-Za-z0-9]*')) =~ str ? 'true' : 'false'  

Answer 1

You can do this by being more particular in your substitutions:

tests = [
  "*.foo",
  "\\*.foo"
]

tests.each do |test|
  r = test.gsub(/(\\\*|\*)/) do |s|
    case ($1)
    when "\\*"
      $1
    else
      "[A-Za-z0-9]*"
    end
  end

  puts r
end

Results for me:

[A-Za-z0-9]*.foo
\*.foo

The first capture looks for \\* specifically.

Answer 2

You can use a Negative Lookbehind assertion here.

"foo\\* bar* baz* quz\\*".gsub(/(?<!\\)\*/, '[A-Za-z0-9]*')
# => 'foo\* bar[A-Za-z0-9]* baz[A-Za-z0-9]* quz\*'