CODEWITHSUNDEEP
ruby-on-railsrubyruby-on-rails-3
Mellon
Mellon

Reputation: 38842

string value checking

I would like to check if a variable's string value is a number string (e.g. '3.2', '1') or alphabet string (e.g. 'abc'), is there any easy way to do this in ruby or Rails 3 ?

Upvotes: 0

Views: 418

Answers (5)

Will Barrett
Will Barrett

Reputation: 2647

I would use Float().

def numeric?(object)
  true if Float(object) rescue false
end

Upvotes: 7

Rein Henrichs
Rein Henrichs

Reputation: 15605

Implementations using Kernel#Float expect and rescue an exception, which is slow and poor design. I would prefer:

class String
  def is_numeric?  
    string.to_f.to_s == string ||
      string.to_i.to_s == string
  end
end

Upvotes: 0

Brandon Montgomery
Brandon Montgomery

Reputation: 6986

You could use regular expressions to help you with this.

str = "abc"
# first regex checks for character string, second regex checks for floating point number
if not str.empty? and str =~ /^[a-z]+$/i or str =~ /^[-+]?[0-9]*\.?[0-9]*$/ then
  # this is a match
else
  # no match
end

I didn't fully test these regexes - you'd have to make sure these fit your needs.

Upvotes: 1

user229044
user229044

Reputation: 239270

You could add a is_numeric? method to the string class:

class String
  def is_numeric?
    true if Float(self) rescue false
  end
end

p "123".is_numeric? # true
p "abc".is_numeric? # false

Using Float() instead of a regular expression handles some weird cases that you might not want to consider "numeric", like +123 or -.3.

Upvotes: 1

Robin Fisher
Robin Fisher

Reputation: 1454

string == /\d+\.?\d+/ ? "Numbers" : "Letters"

Upvotes: -2

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