Question

I’m trying to figure out how to check if a string matches a regular expression, but I want to know if the entire string matches just once. Here’s my code but it seems absurdly long

def single_match(test_me, regex)   ret_val = false   test = regex.match(test_me)   if (test.length==1 && test[0].length == test_me.length)       ret_val = true   end   return ret_val end 

is there an easier way to do this?

P.S. Here’s the method I’m really trying to write, since people always seem to ask why I want the gun these days:

def is_int(test_me)   return single_match(test_me, /[0-9]*/) end 

Edit Thanks everybody. Here’s where I’m really using it, but this regex stuff is always interesting to go through. Thanks for the great and educational answers.

Answer 1

You don’t need to do this, your method can be replaced by using the regular expression of /^[0-9]*$/. The ^ tells it match start of a line and $ tells it match end of the line. So it will match: start of line, 0 to any in range of 0 to 9, and finally end of line.

def is_int(test_me)   test_me =~ /^[0-9]*$/ end 

And you don’t need the return statements, Ruby implicitly returns the last statement.

Edit:

It probably would be easier and look better to use the to_i instance method of String class.

def is_int(test_me)   test_me.to_i.to_s == test_me end 

Edit: (did some tests)

Comparing the performance between the two methods shows that .to_i.to_s == way is 5% faster. So it is up to personal preference to which ever looks better and if you want to handle leading zeroes.