Ruby-on-rails 如何检查值是否为数字？
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How can I check if a value is a number?
提问by user211662
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?
我只想检查表单文本字段的返回值是否是数字，即： 12 、 12.5 或 12.75 。有没有一种简单的方法来检查这一点，尤其是当值被拉为 a 时param？
采纳答案by cwninja
Just regexp it, it's trivial, and not worth thinking about beyond that:
只需对其进行正则表达式，这很简单，除此之外不值得考虑：
v =~ /\A[-+]?[0-9]*\.?[0-9]+\Z/
(Fixed as per Justin's comment)
（根据贾斯汀的评论修复）
回答by Peter
You can use
您可以使用
12.is_a? Numeric
(Numericwill work for integers and floats.)
（Numeric适用于整数和浮点数。）
If it arrives as a string that might contain a representation of a valid number, you could use
如果它作为可能包含有效数字表示的字符串到达，则可以使用
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).
然后'12'.valid_float?将返回 true 如果您可以将字符串转换为有效的浮点数（例如 with to_f）。
回答by daesu
I usually just use Integer and Float these days.
这些天我通常只使用 Integer 和 Float 。
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
回答by ryanprayogo
You can add a:
您可以添加一个：
validates_numericality_of :the_field
in your model.
在你的模型中。
See: http://api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#M002172
请参阅：http: //api.rubyonrails.org/classes/ActiveRecord/Validations/ClassMethods.html#M002172
回答by Evan Ross
Just convert string twice:
只需将字符串转换两次：
num = '12'
num == num.to_i.to_s
#=> true
num = '3re'
num == num.to_i.to_s
#=> false
回答by Brian Armstrong
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
回答by installero
I would suggest this one
我会推荐这个
def is_number?
self.to_f == self
end
> 15.is_number?
=> true
> 15.0.is_number?
=> true
> 'Not a number'.is_number?
=> false
> (0/0.0).is_number?
=> false
回答by Adrian Teh
String values always convert to 0 with .to_i
字符串值总是使用 .to_i 转换为 0
[14] pry(main)> 'Apple'.to_i > 0
=> false
[15] pry(main)> '101'.to_i > 0
=> true
