Check if given string is an URL

def uri?(string)  uri = URI.parse(string)  %w( http https ).include?(uri.scheme)rescue URI::BadURIError  falserescue URI::InvalidURIError  falseend

This is a very simple example. The advantage of using the URI library over a regular expression is that you can perform complex checks.

ruby-on-rails ruby regex

validates :url, :format => URI::regexp(%w(http https))

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