Question

or even better can I do hash.has_key?('videox') where x is

• ” nothing or
• a digit?

so ‘video’, ‘video1’, ‘video2’ would pass the condition?

of course I can have two conditions but in case I need to use video3 in the future things would get more complicated…

Answer 1

If you want the general case of video followed by a digit without explicitly listing all the combinations there are a couple of methods from Enumerable that you could use in combination with a regular expression.

hash.keys is an array of the keys from hash and ^video\d$ matches video followed by a digit.

# true if the block returns true for any element    
hash.keys.any? { |k| k.match(/^video\d$/ }

or

# grep returns an array of the matching elements
hash.keys.grep(/^video\d$/).size > 0

grep would also allow you to capture the matching key(s) if you needed that information for the next bit of your code e.g.

if (matched_keys = hash.keys.grep(/^video\d$/)).size > 0
  puts "Matching keys #{matched_keys.inspect}"

Furthermore, if the prefix of key we’re looking for is in a variable rather than a hard coded string we can do something along the lines of:

prefix = 'video'
# use an interpolated string, note the need to escape the
# \ in \d
hash.keys.any? { |k| k.match("^#{prefix}\\d$") }