I want to use grep with a string as regex pattern. How can i do that?
Example:
myArray.grep(/asd/i) #Works perfectly.
But i want to prepare my statement first
searchString = '/asd/i'
myArray.grep(searchString) # Fails
How can i achieve this? I need a string prepared because this is going into a search algorithm and query is going to change on every request. Thanks.
Regular expressions support interpolation, just like strings:
var = "hello"
re = /#{var}/i
p re #=> /hello/i
/#{Regexp.escape(user_provided_string)}/i or Regexp.new(Regexp.escape(user_provided_string), "i"). This would for example treat a "." as a literal "." character and not as "any character". As a short but cryptic way to both escape a string and turn it into a regex, you can do Regexp.union(user_provided_string).Having something in quotes is not the same as the thing itself. /a/i is Regexp, "/a/i" is string. To construct a Regexp from string do this:
r = Regexp.new str
myArray.grep(r)
Edit:
I found a better way
myString = "Hello World!"
puts "Hello World!"
puts "Enter word to search"
input_search = gets.chomp
puts "Search insensitive? y/n"
answer = gets.chomp
if answer == "y"
ignore = "Regexp::IGNORECASE"
else
ignore = false
end
puts myString.lines.grep(Regexp.new(input_search, ignore))
My old Answer below:
Try making it a case or if statement passing if they want insensitive search on or off, etc
myString = "Hello World!"
puts "Enter word to search"
input_search = gets.chomp
puts "Search insensitive? y/n"
case gets.chomp
when "y"
puts myString.lines.grep(Regexp.new(/#{input_search}/i))
when "n"
puts myString.lines.grep(Regexp.new(/#{input_search}/))
end
'/asd/i' is a String. Why not make it a Regrexp? If you need to go from String to Regexp one way to do so is by creating a new Regexp object:
>> re = Regexp.new('/asd/i')
=> /\/asd\/i/
>> re = Regexp.new("asd", "i")
=> /asd/i
So perhaps,
>> str = gets.chomp #user inputs
=> "Hello World"
re = Regexp.new(str, "i")
=> /Hello World/i
is what you're looking for.
But overall I don't think you can simply "use a string as a regexp pattern", though I'm a beginner and may be wrong about this.
