Rails: Why is the "number_with_delimiter" method not recognized inside my model?

Question

I have a simple validation:

class Product < ActiveRecord::Base
  # include ActionView::Helpers::NumberHelper
  ...
  validates_numericality_of :price, :less_than => 1000000, 
                            :message => "must be less than #{number_with_delimiter(1000000)}"                       
  ...
end

On this code, I have received the following error:

undefined method `number_with_delimiter' for #<Class:0x2665a58>

I tried to add:

include ActionView::Helpers::NumberHelper

but it didn't help.

What am I missing?

score 19 · Accepted Answer · edited May 26 '21 at 13:40

19

The true problem here is that you're including this module into the class, rather than extended the class with it.

The differences is an include will make the methods available on the instance, where as the extend will make them where you're trying to use them: on the class.

For instance method use

include ActionView::Helpers::NumberHelper

For class method use

extend ActionView::Helpers::NumberHelper

edited May 26 '21 at 13:40

Ahmad Hussain

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answered Dec 17 '10 at 04:47

Ryan Bigg

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@Ryan: I understand that including inside the class is equivalent to defining my own methods in this class, right ? Does this means that I could use `self.number_with_delimiter(...)` ? When you put the `include` outside the class, are all methods inside `ActionView::Helpers::NumberHelper` becomes global ? – Misha Moroshko Dec 17 '10 at 09:01
@Misha: Yes they'd become global but that's generally Not A Good Idea(tm). Best thing to do in this case is to `extend` the class with the module. – Ryan Bigg Dec 17 '10 at 10:27
@Ryan: How do I extend the `Product` class with the `NumberHelper` module ? Isn't this what I did above ? – Misha Moroshko Dec 17 '10 at 12:42
@Misha: No, you're `include`'ing the module. `extend` is different. – Ryan Bigg Dec 17 '10 at 13:58
@Ryan: I'm confused. Including the module in model's class is exactly what I did above, and it didn't work. It worked, however, when I moved the `include` outside the class. – Misha Moroshko Dec 18 '10 at 02:04

score 5 · Answer 2 · answered Sep 22 '14 at 17:00

5

Instead of extending ActionView module. You can use methods from ActiveSupport instead

For example:

ActiveSupport::NumberHelper::number_to_currency(10000.1234,{precision: 2,unit: ''})

answered Sep 22 '14 at 17:00

Le Duc Duy

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is that better from a performance standpoint in terms of memory usage? – Ninjaxor Feb 25 '16 at 18:43

score 3 · Answer 3 · edited Aug 12 '17 at 16:28

3

You should use extend:

Usage: extend ActionView::Helpers::NumberHelper

It is good for me

edited Aug 12 '17 at 16:28

Tallboy

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answered May 14 '12 at 11:17

taivn07

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Bnjmn · Answer 4 · 2010-12-17T04:41:57.000

2

You might be missing the dependency... is the NumberHelper class accessible to your application?

Check the official Rails docs

edited Dec 17 '10 at 04:41

answered Dec 17 '10 at 04:32

Bnjmn

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score 2 · Answer 5 · answered Jan 21 '20 at 08:45

2

good answer, use :

ActiveSupport::NumberHelper::number_to_delimited(number, options={})

answered Jan 21 '20 at 08:45

Matrix

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Rails: Why is the "number_with_delimiter" method not recognized inside my model?

5 Answers5

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