How to grep elements in array that match patterns from another array?

Question

I have two arrays:

a = ["X2", "X3/X4", "X5/X6/X7", "X8/X9/X10/X11"]
b = ["X9/X10", "X3/X4"]

Now I need to select entries from 'a' array which regexp with any of entries from array 'b'.

Expected result is:

["X3/X4", "X8/X9/X10/X11"]

How can I do this in Ruby?

Answer 1

I'd do:

a.grep(Regexp.union(b))
# => ["X3/X4", "X8/X9/X10/X11"] 

Answer 2

This should work:

a.grep(/#{b.join('|')}/)
# => ["X3/X4", "X8/X9/X10/X11"]

Answer 3

Try the below:

 a = ["X2", "X3/X4", "X5/X6/X7", "X8/X9/X10/X11"] 
 b = ["X9/X10", "X3/X4"]
 p a.select{|i| b.any?{|j| i.include? j }}
 #>> ["X3/X4", "X8/X9/X10/X11"]

Answer 4

The safest way is to build a regular expression and then select elements of your array matching this expression:

Regexp.union("a", "b", "c")
# => /a|b|c/

Regexp.union(["a", "b", "c"])
# => /a|b|c/

("b".."e").to_a.grep(Regexp.union("a", "b", "c"))
# => ["b", "c"]