Ruby: Checking if a string is all letters

Looking at the stats on my previous post, I noticed a lot of people are wrongly redirected when they’re looking for a solution to check if a ruby string is all letters. For those, I’d like to post my solution, which is imo a clean way of doing it:

def all_letters(str)
	# Use 'str[/[a-zA-Z]*/] == str' to let all_letters
	# yield true for the empty string
	str[/[a-zA-Z]+/]  == str
end

Analogous, we can do this with digits as well:

def all_digits(str)
	str[/[0-9]+/]  == str
end

def all_letters_or_digits(str)
	str[/[a-zA-Z0-9]+/]  == str
end

Of course, it’s even better if you make these methods a core extension of String itself

~ by moiristo on June 4, 2009.