CODEWITHSUNDEEP
ruby-on-railsruby
user211662
user211662

Reputation: 18427

How can I check if a value is a number?

I want to simply check if a returned value from a form text field is a number i.e.: 12 , 12.5 or 12.75. Is there a simple way to check this, especially if the value is pulled as a param?

Upvotes: 112

Views: 121934

Answers (10)

Kiryl Plyashkevich
Kiryl Plyashkevich

Reputation: 2267

I'd rather use regexp matching, for example:

irb(main):015:0> 12.5.to_s.match?(/^-?\d+(\.\d+)?$/)
=> true

Upvotes: 0

installero
installero

Reputation: 9776

I would suggest this one

def is_a_number?(str)
  !!(Float(str) rescue false)
end

> is_a_number?(1)
 => true

> is_a_number?(1.1)
 => true 

> is_a_number?('1')
 => true 

> is_a_number?('1.1')
 => true 

> is_a_number?('a')
 => false 

> is_a_number?(nil)
 => false

Upvotes: 6

mechnicov
mechnicov

Reputation: 15258

There was answer with Kernel#Float

But this variant is used with exception: false key and double bang to return boolean

class String
  def number?
    !!Float(self, exception: false)
  end
end

Upvotes: 1

Vlad Hilko
Vlad Hilko

Reputation: 1244

Just convert string twice:

num = '12'
num == num.to_i.to_s 
#=> true 

num = '3re'
num == num.to_i.to_s 
#=> false

Upvotes: 12

Adrian Teh
Adrian Teh

Reputation: 1967

String values always convert to 0 with .to_i

[14] pry(main)> 'Apple'.to_i > 0
=> false

[15] pry(main)> '101'.to_i > 0
=> true

Upvotes: -6

Peter
Peter

Reputation: 132227

You can use

12.is_a? Numeric

(Numeric will work for integers and floats.)

If it arrives as a string that might contain a representation of a valid number, you could use

class String
  def valid_float?
    true if Float self rescue false
  end
end

and then '12'.valid_float? will return true if you can convert the string to a valid float (e.g. with to_f).

Upvotes: 246

cwninja
cwninja

Reputation: 9778

Just regexp it, it's trivial, and not worth thinking about beyond that:

v =~ /\A[-+]?[0-9]*\.?[0-9]+\Z/

(Fixed as per Justin's comment)

Upvotes: 30

Brian Armstrong
Brian Armstrong

Reputation: 19863

irb(main):005:0> 1.1.is_a? Numeric
=> true
irb(main):006:0> 1.is_a? Numeric
=> true
irb(main):007:0> 'asd'.is_a? Numeric
=> false

Upvotes: 4

daesu
daesu

Reputation: 620

I usually just use Integer and Float these days.

1.9.2p320 :001 > foo = "343"
 => "343"
1.9.2p320 :003 > goo = "fg5"
 => "fg5"

1.9.2p320 :002 > Integer(foo) rescue nil
 => 343
1.9.2p320 :004 > Integer(goo) rescue nil
 => nil

1.9.2p320 :005 > Float(foo) rescue nil
 => 343.0
1.9.2p320 :006 > Float(goo) rescue nil
 => nil

Upvotes: 32

ryanprayogo
ryanprayogo

Reputation: 11817

You can add a:

validates_numericality_of :the_field

in your model.

See: http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#M002172

Upvotes: 16

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