Ruby: What's the proper syntax for a boolean regex method?

Question

What is the proper syntax for a method that checks a string for a pattern, and returns true or false if the regex matches?

Basic idea:

def has_regex?(str         


        

Answer 1

As I wanted this to work generally, and not just for any specific project, I do not want to modify the environment at all.

I was able to get it to work by simply using the return value from the normal match method as a conditional. Tested both the positive and negative case on this sample string:

irb(main):014:0> if "123".match(/.2./); puts "worked"; end
worked
=> nil
irb(main):015:0> if "123".match(/.3./); puts "worked"; end
=> nil

Answer 2

To make it return true/false switch the position of pattern and string and use case equality ===

def has_regex?(string)
    pattern = /something/i
    return pattern === string
end

I absolutely needed it to return true boolean value and digged around. It is actually documented in regexp class http://www.ruby-doc.org/core-2.1.3/Regexp.html#method-i-3D-3D-3D

Answer 3

If you want the put the pattern in a method, you can just do

def has_my_pattern(st)
    st =~ /pattern/
end

Or, perhaps better, put the pattern in a class variable instead?

Answer 4

For Ruby >= 2.4 or Rails, you can do:

 regexp.match?(string)

Answer 5

For anyone's future reference, double bangs are frowned upon from bbatsov's ruby style guide. Instead of using a double bang, just check if the value isn't nil. If the value isn't nil, it exists.

Instead of doing this:

def has_regex?(string)
  !!(string =~ /something/i)
end

You can always do this:

def has_regex?(string)
  !(string =~ /something/i).nil?
end

Answer 6

Your code looks fine, but you could write it even smaller.

The return value of String#=~ behaves this way:

• nil if the pattern did not match
• the position in the string where the matched word started

In Ruby everything except nil and false behaves like true in a conditional statement so you can just write

if string=~ pattern
  # do something
else
  # panic
end