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LED

2012-Feb-21 07:15 UTC

nil can''t be coerced into BigDecimal

hi guys im playing with RoR with the environment of rails 3 ruby 1.9 i
got stuck in

nil can''t be coerced into BigDecimal

error

i need to get the total cost of the products inside the cart i know
where the problem is(i think) but i almost did every thing
cart/show.html.rb

<div class="cart_title" >Your Cart</div>
    <table>
        <% for item in @cart.line_items %>
    <tr>
        <td><%= item.quantity %>&times;</td>
        <td><%= item.product.title %></td>
    <td class="item_price" ><%=
number_to_currency(item.total_price)
%></td>
    </tr>
    <% end %>
        <tr class="total_line" >
        <td colspan="2" >Total</td>
        <td class="total_cell"
><%number_to_currency(@cart.total_price) %></td>
    </tr>
    </table>
        <%= button_to ''Empty cart'', @cart, :method =>
:delete,
        :confirm => ''Are you sure?'' %>

model/line_item.rb

  def total_price
    line_items.to_a.sum { |item| item.total_price }
  end
model/cart.rb

 def total_price
    product.price  * quantity
  end
my second option is

def total_price
     if product.price
       product.price * quantity
     else
       product.price = "0.0".to_d
     end
   end
but still this wont work

thanks more power to us!

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Peter Vandenabeele

2012-Feb-21 08:32 UTC

head link

Re: nil can''t be coerced into BigDecimal

On Tue, Feb 21, 2012 at 8:15 AM, LED
<leedapdap-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> hi guys im playing with RoR with the environment of rails 3 ruby 1.9 i
> got stuck in
>
> nil can''t be coerced into BigDecimal
>
> error
>
> i need to get the total cost of the products inside the cart i know
> where the problem is(i think) but i almost did every thing
> cart/show.html.rb
>
> <div class="cart_title" >Your Cart</div>
>    <table>
>        <% for item in @cart.line_items %>
>    <tr>
>        <td><%= item.quantity %>&times;</td>
>        <td><%= item.product.title %></td>
>    <td class="item_price" ><%=
number_to_currency(item.total_price)
> %></td>
>    </tr>
>    <% end %>
>        <tr class="total_line" >
>        <td colspan="2" >Total</td>
>        <td class="total_cell" ><%>
number_to_currency(@cart.total_price) %></td>
>    </tr>
>    </table>
>        <%= button_to ''Empty cart'', @cart, :method
=> :delete,
>        :confirm => ''Are you sure?'' %>
>
> model/line_item.rb
>
>  def total_price
>    line_items.to_a.sum { |item| item.total_price }
>  end
> model/cart.rb
>
>  def total_price
>    product.price  * quantity
>  end
> my second option is
>
> def total_price
>     if product.price
>       product.price * quantity
>     else
>       product.price = "0.0".to_d
>
This code is assigning a 0 to fixed price of a product
(most probably not what is intended). Probably simply
return a 0 (in BigDecimal) here.

>     end
>   end
> but still this wont work
>
Is there a business rule that each item must realistically have
a quantity and product (and that product must have a price) ?

In that case I suggest:

* add validations for the presence of these values
  (presence of quantity and product on item
   presence of price on product)

* write code like:

def total_price
    if self.valid?
      product.price * quantity
    else
      0.to_d
    end
  end


Another possible gotcha is that "item.product_id" is available
(e.g. from a select box), but item.product is not yet associated
(you may need to override the product_id= setter for that  e.g.

def product_id=(product_id)
  self.product = Product.find_by_id(product_id)
  super
end

HTH,

Peter


-- 
*** Available for a new project ***

Peter Vandenabeele
http://twitter.com/peter_v
http://rails.vandenabeele.com
http://coderwall.com/peter_v

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LED

2012-Feb-21 08:48 UTC

head link

Re: nil can''t be coerced into BigDecimal

>> Is there a business rule that each item must realistically have
>> a quantity and product (and that product must have a price) ?
uhm im following agile web development rails actualy the snippets are
from the book

> * add validations for the presence of these values
>   (presence of quantity and product on item
>    presence of price on product)i already validated the price
of each item in CRUD

model/product.rb
  validates :price, :numericality => {:greater_than_or_equal_to =>
0.01}


im trying to to follow your suggestion but nothing happens it was
still the same as it was :(


On Feb 21, 4:32 pm, Peter Vandenabeele
<pe...-jNuWw7i2w7syMbTcgqFhxg@public.gmane.org>
wrote:> On Tue, Feb 21, 2012 at 8:15 AM, LED
<leedap...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > hi guys im playing with RoR with the environment of rails 3 ruby 1.9 i
> > got stuck in
>
> > nil can''t be coerced into BigDecimal
>
> > error
>
> > i need to get the total cost of the products inside the cart i know
> > where the problem is(i think) but i almost did every thing
> > cart/show.html.rb
>
> > <div class="cart_title" >Your Cart</div>
> >    <table>
> >        <% for item in @cart.line_items %>
> >    <tr>
> >        <td><%= item.quantity %>&times;</td>
> >        <td><%= item.product.title %></td>
> >    <td class="item_price" ><%=
number_to_currency(item.total_price)
> > %></td>
> >    </tr>
> >    <% end %>
> >        <tr class="total_line" >
> >        <td colspan="2" >Total</td>
> >        <td class="total_cell"
><%=>number_to_currency(@cart.total_price)%></td>
> >    </tr>
> >    </table>
> >        <%= button_to ''Empty cart'', @cart, :method
=> :delete,
> >        :confirm => ''Are you sure?'' %>
>
> > model/line_item.rb
>
> >  def total_price
> >    line_items.to_a.sum { |item| item.total_price }
> >  end
> > model/cart.rb
>
> >  def total_price
> >    product.price  * quantity
> >  end
> > my second option is
>
> > def total_price
> >     if product.price
> >       product.price * quantity
> >     else
> >       product.price = "0.0".to_d
>
> This code is assigning a 0 to fixed price of a product
> (most probably not what is intended). Probably simply
> return a 0 (in BigDecimal) here.
>
> >     end
> >   end
> > but still this wont work
>
> Is there a business rule that each item must realistically have
> a quantity and product (and that product must have a price) ?
>
> In that case I suggest:
>
> * add validations for the presence of these values
>   (presence of quantity and product on item
>    presence of price on product)
>
> * write code like:
>
> def total_price
>     if self.valid?
>       product.price * quantity
>     else
>       0.to_d
>     end
>   end
>
> Another possible gotcha is that "item.product_id" is available
> (e.g. from a select box), but item.product is not yet associated
> (you may need to override the product_id= setter for that  e.g.
>
> def product_id=(product_id)
>   self.product = Product.find_by_id(product_id)
>   super
> end
>
> HTH,
>
> Peter
>
> --
> *** Available for a new project ***
>
> Peter
Vandenabeelehttp://twitter.com/peter_vhttp://rails.vandenabeele.comhttp://coderwall.com/peter_v
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Peter Vandenabeele

2012-Feb-21 08:51 UTC

head link

Re: Re: nil can''t be coerced into BigDecimal

On Tue, Feb 21, 2012 at 9:48 AM, LED
<leedapdap-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> >> Is there a business rule that each item must realistically have
> >> a quantity and product (and that product must have a price) ?
>
> uhm im following agile web development rails actualy the snippets are
> from the book
>
>
> > * add validations for the presence of these values
> >   (presence of quantity and product on item
> >    presence of price on product)
> i already validated the price
> of each item in CRUD
>
> model/product.rb
>  validates :price, :numericality => {:greater_than_or_equal_to =>
> 0.01}
>
>For clarity. It is not because a validation is present that the
value is always present in memory (in the database, using the
standard techniques for saving, only valid data should ever be
really saved).

Is the data for the item valid?
* quantity
* product
* product_id

Check out the values of those 3.

HTH,

Peter

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LED

2012-Feb-21 08:56 UTC

head link

Re: nil can''t be coerced into BigDecimal

yes those data are valid actualy a while ago it worked but when i
clear and destroy the cart it returned to this error
very much appreciated for your effort thank you

On Feb 21, 4:51 pm, Peter Vandenabeele
<pe...-jNuWw7i2w7syMbTcgqFhxg@public.gmane.org>
wrote:> On Tue, Feb 21, 2012 at 9:48 AM, LED
<leedap...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> > >> Is there a business rule that each item must realistically
have
> > >> a quantity and product (and that product must have a price) ?
>
> > uhm im following agile web development rails actualy the snippets are
> > from the book
>
> > > * add validations for the presence of these values
> > >   (presence of quantity and product on item
> > >    presence of price on product)
> > i already validated the price
> > of each item in CRUD
>
> > model/product.rb
> >  validates :price, :numericality => {:greater_than_or_equal_to
=>
> > 0.01}
>
> For clarity. It is not because a validation is present that the
> value is always present in memory (in the database, using the
> standard techniques for saving, only valid data should ever be
> really saved).
>
> Is the data for the item valid?
> * quantity
> * product
> * product_id
>
> Check out the values of those 3.
>
> HTH,
>
> Peter
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ruby LED

2012-Feb-21 09:00 UTC

head link

Re: nil can''t be coerced into BigDecimal

app/models/line_item.rb:24:in `*''
app/models/line_item.rb:24:in `total_price''
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/home/led/.rvm/rubies/ruby-1.9.2-p290/lib/ruby/1.9.1/webrick/server.rb:183:in 
`block in start_thread''


its the full trace of the error cant seems to find it im a week old in 
ruby on rails development

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Valery Kvon

2012-Feb-21 09:03 UTC

head link

Re: nil can''t be coerced into BigDecimal

On 21.02.2012, at 11:15, LED wrote:
> hi guys im playing with RoR with the environment of rails 3 ruby 1.9 i
> got stuck in
> 
> nil can''t be coerced into BigDecimal
> 
>   def total_price
>    line_items.to_a.sum { |item| item.total_price }
>  end
> model/cart.rb
> 
That error would be expected when some of line_items.total_price returns nil.
Moreover you can sum total prices without .to_a, that would be more efficient.

> def total_price
>    product.price  * quantity
>  end
> 
> def total_price
>     if product.price
>       product.price * quantity
>     else
>       product.price = "0.0".to_d	It is not necessary to write attribute :price, just let it return zero. 0.to_d
in this case.
	>     end
>   end
Now. before test it again, check in the database if any product has a nil or any
non-bigdecimal value.

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ruby LED

2012-Feb-21 09:17 UTC

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Re: nil can''t be coerced into BigDecimal

>> nil can''t be coerced into BigDecimal
>>
>>   def total_price
>>    line_items.to_a.sum { |item| item.total_price }
>>  end
>> model/cart.rb
>>
>
> That error would be expected when some of line_items.total_price returns
> nil. Moreover you can sum total prices without .to_a, that would be more
> efficient.tried to applying this but gotting the problem in the
view>
>> def total_price
>>    product.price  * quantity
>>  end
>>
>> def total_price
>>     if product.price
>>       product.price * quantity
>>     else
>>       product.price = "0.0".to_d
>   It is not necessary to write attribute :price, just let it return
> zero. 0.to_d in this case.i tried this and it worked out but when reseting the cart it return the
error>>     end
>>   end
> Now. before test it again, check in the database if any product has a
> nil or any non-bigdecimal value.
this is being weird when i tried your suggestion it worked out but when
i
clear delete the cart again it return to the error :(

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ruby LED

2012-Feb-21 09:21 UTC

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Re: nil can''t be coerced into BigDecimal

i tried refactoring my destroy method now its working fine but my second 
issue is when i add item to the cart at first attemp it returns to that 
error again but returning to the product list it worked fine im just 
wondering if my add_product is code is ok?

def add_product(product_id)
    current_item = line_items.where(:product_id => product_id).first

     if current_item
        current_item.quantity = current_item.quantity.to_i + 1
      else
        current_item = LineItem.new(:product_id=>product_id)
        line_items << current_item
      end
        current_item
   end

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Valery Kvon

2012-Feb-21 09:24 UTC

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Re: Re: nil can''t be coerced into BigDecimal

I didn''t see you code completely, but

line_items.to_a.sum { |item| item.total_price }

How can it count correct if only ONE item in the cart? :)

Obviously, if you want to get Array, use Array.wrap method like this:

Array.wrap(line_items).sum { |item| item.total_price }



On 21.02.2012, at 13:21, ruby LED wrote:
> i tried refactoring my destroy method now its working fine but my second 
> issue is when i add item to the cart at first attemp it returns to that 
> error again but returning to the product list it worked fine im just 
> wondering if my add_product is code is ok?
> 
> def add_product(product_id)
>    current_item = line_items.where(:product_id => product_id).first
> 
>     if current_item
>        current_item.quantity = current_item.quantity.to_i + 1
>      else
>        current_item = LineItem.new(:product_id=>product_id)
>        line_items << current_item
>      end
>        current_item
>   end
> 
> 
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ruby LED

2012-Feb-21 09:39 UTC

head link

Re: Re: nil can''t be coerced into BigDecimal

Valery Kvon wrote in post #1047975:> I didn''t see you code completely, but
>
> line_items.to_a.sum { |item| item.total_price }
>
> How can it count correct if only ONE item in the cart? :)
>
> Obviously, if you want to get Array, use Array.wrap method like this:
>
> Array.wrap(line_items).sum { |item| item.total_price }
i tried Array.wrap(line_items).sum { |item| item.total_price }
also it worked same as the
line_items.to_a.sum { |item| item.total_price }
(i think?)
but im having the issue of not counting my first attemp maybe my 
add_product code is wrong?

def add_product(product_id)
    current_item = line_items.where(:product_id => product_id).first

     if current_item
        current_item.quantity = current_item.quantity.to_i + 1
      else
        current_item = LineItem.new(:product_id=>product_id)
        line_items << current_item
      end
        current_item
   end

it feels like im adding a nil value at my first attemp of adding a 
product into my cart?
btw thanks for your concern with my post :)

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Colin Law

2012-Feb-21 09:45 UTC

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Re: Re: Re: nil can''t be coerced into BigDecimal

On 21 February 2012 09:39, ruby LED
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org>
wrote:> Valery Kvon wrote in post #1047975:
>> I didn''t see you code completely, but
>>
>> line_items.to_a.sum { |item| item.total_price }
>>
>> How can it count correct if only ONE item in the cart? :)
>>
>> Obviously, if you want to get Array, use Array.wrap method like this:
>>
>> Array.wrap(line_items).sum { |item| item.total_price }
>
> i tried Array.wrap(line_items).sum { |item| item.total_price }
> also it worked same as the
> line_items.to_a.sum { |item| item.total_price }
> (i think?)
> but im having the issue of not counting my first attemp maybe my
> add_product code is wrong?
>
> def add_product(product_id)
>    current_item = line_items.where(:product_id => product_id).first
>
>     if current_item
>        current_item.quantity = current_item.quantity.to_i + 1
>      else
>        current_item = LineItem.new(:product_id=>product_id)
>        line_items << current_item
>      end
>        current_item
>   end
>
> it feels like im adding a nil value at my first attemp of adding a
> product into my cart?
It is not the item that is nil but total_price.  If it were the item
that were nil then you would get an error saying that nil did not have
a method total_price.  Where are you setting total_price when you do
LineItem.new.

Colin

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Valery Kvon

2012-Feb-21 09:48 UTC

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Re: nil can''t be coerced into BigDecimal

> 
> def add_product(product_id)
>    current_item = line_items.where(:product_id => product_id).first
> 
>     if current_item
>        current_item.quantity = current_item.quantity.to_i + 1
>      else
>        current_item = LineItem.new(:product_id=>product_id)
>        line_items << current_item
	Ok, let''s imagine. You add new LineItem and product.price is nil or
quantity is nil
	then 
	product.price * quantity
	would raise error "nil can''t be coerced into…"

	Check if product price or quantity is nil after initialize LineItem.new
>      end
>        current_item
>   end
> 
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ruby LED

2012-Feb-21 09:55 UTC

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Re: Re: Re: nil can''t be coerced into BigDecimal

Colin Law wrote in post #1047978:> On 21 February 2012 09:39, ruby LED
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
>>
>> it feels like im adding a nil value at my first attemp of adding a
>> product into my cart?
>
> It is not the item that is nil but total_price.  If it were the item
> that were nil then you would get an error saying that nil did not have
> a method total_price.  Where are you setting total_price when you do
> LineItem.new.
>i belive im setting it in the current_item it self
current_item = LineItem.new(:product_id=>product_id)> Colin
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Valery Kvon

2012-Feb-21 10:00 UTC

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Re: Re: Re: Re: nil can''t be coerced into BigDecimal

Show us the code of LineItem class.


This method raises the error on a new instance. To avoid it, it must return
BigDec anytime. In your case product.price is nil or quantity is nil..

def total_price
   product.price  * quantity
end


On 21.02.2012, at 13:55, ruby LED wrote:
> Colin Law wrote in post #1047978:
>> On 21 February 2012 09:39, ruby LED
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
>>> 
>>> it feels like im adding a nil value at my first attemp of adding a
>>> product into my cart?
>> 
>> It is not the item that is nil but total_price.  If it were the item
>> that were nil then you would get an error saying that nil did not have
>> a method total_price.  Where are you setting total_price when you do
>> LineItem.new.
>> 
> i belive im setting it in the current_item it self
> current_item = LineItem.new(:product_id=>product_id)
>> Colin
> 
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Peter Vandenabeele

2012-Feb-21 10:05 UTC

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Re: Re: Re: Re: nil can''t be coerced into BigDecimal

On Tue, Feb 21, 2012 at 10:55 AM, ruby LED
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
> Colin Law wrote in post #1047978:
> > On 21 February 2012 09:39, ruby LED
<lists-fsXkhYbjdPsEEoCn2XhGlw@public.gmane.org> wrote:
> >>
> >> it feels like im adding a nil value at my first attemp of adding a
> >> product into my cart?
> >
> > It is not the item that is nil but total_price.  If it were the item
> > that were nil then you would get an error saying that nil did not have
> > a method total_price.  Where are you setting total_price when you do
> > LineItem.new.
> >
> i belive im setting it in the current_item it self
> current_item = LineItem.new(:product_id=>product_id)
>
As I wrote above. This sets the product_id, but not
necessarily the "product" association. Check values of
* current_item.product_id
* current_item.product
right after this line.

HTH,

Peter

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ruby LED

2012-Feb-21 10:08 UTC

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Re: Re: Re: Re: nil can''t be coerced into BigDecimal

Valery Kvon wrote in post #1047982:> Show us the code of LineItem class.
>
>
> This method raises the error on a new instance. To avoid it, it must
> return BigDec anytime. In your case product.price is nil or quantity is
> nil..
>
> def total_price
>    product.price  * quantity
> end
class LineItem < ActiveRecord::Base
  belongs_to :product
  belongs_to :cart

  def total_price
     if product.price
       product.price = product.price * quantity
     else
        0.to_d
     end
   end
end

this is my model/line item.rb

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Valery Kvon

2012-Feb-21 10:30 UTC

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Re: Re: Re: Re: Re: nil can''t be coerced into BigDecimal

On 21.02.2012, at 14:08, ruby LED wrote:
> class LineItem < ActiveRecord::Base
>  belongs_to :product
>  belongs_to :cart
> 
>  def total_price
>     if product.price
>       product.price = product.price * quantity
>     else
>        0.to_d
>     end
>   end
> end
> 
So.

I agree that:
1) current_item = LineItem.new(:product_id=>product_id) = BAD IDEA. Because,
if you pass the invalid product ID, LineItem would be initialized as well, but
the .product association would return nil.

2) Actually I didn''t see how quantity is set up? Looking at your
previous code it must be method ''quantity''.

PS. Why are you writing product.price=?

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ruby LED

2012-Feb-21 11:29 UTC

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Re: Re: Re: Re: Re: nil can''t be coerced into BigDecimal

Valery Kvon wrote in post #1047990:> On 21.02.2012, at 14:08, ruby LED wrote:
>
>>   end
>> end
>>
>
> So.
>
> I agree that:
> 1) current_item = LineItem.new(:product_id=>product_id) = BAD IDEA.
> Because, if you pass the invalid product ID, LineItem would be
> initialized as well, but the .product association would return nil.do you think current_item = line_items.build(:product_id => product_id) 
is better?> 2) Actually I didn''t see how quantity is set up? Looking at your
> previous code it must be method ''quantity''.
 i dont have a method quantity> PS. Why are you writing product.price=?i belive it is same with product.price * quantity
to show the sum of all products inside my cart

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Valery Kvon

2012-Feb-21 15:19 UTC

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Re: nil can''t be coerced into BigDecimal

On 21.02.2012, at 15:29, ruby LED wrote:
> Valery Kvon wrote in post #1047990:
>> 
>> 
>> I agree that:
>> 1) current_item = LineItem.new(:product_id=>product_id) = BAD IDEA.
>> Because, if you pass the invalid product ID, LineItem would be
>> initialized as well, but the .product association would return nil.
> do you think current_item = line_items.build(:product_id => product_id) 
> is better?
no, the correct way is: 

product = Product.find(product_id) # it will raise AcriveRecord::RecordNotFound
if invalid product_id passed.
current_item = LineItem.new(:product => product) # or current_item =
LineItem.new; current_item.product = product

>> 2) Actually I didn''t see how quantity is set up? Looking at
your
>> previous code it must be method ''quantity''.
> i dont have a method quantity
In this case it does not work ever. def total_count - is an instance method.
If you use ''quantity'', so it just MUST be an another instance
method or local variable. There is something wrong with app''s logic.

>> PS. Why are you writing product.price=?
> i belive it is same with product.price * quantity
> to show the sum of all products inside my cart
Logic, logic, logic….

 product - is a stand alone instance or One product. Why Would it ever have the
multiplied price with ''quantity'' ?.


I remember many years ago I read the beginner''s book "Agile Web
Development with Rails", is that example from it? I think you missed
something.

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ruby LED

2012-Feb-21 15:33 UTC

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Re: nil can''t be coerced into BigDecimal

>
>>> PS. Why are you writing product.price=?
>> i belive it is same with product.price * quantity
>> to show the sum of all products inside my cart
>
> Logic, logic, logic.
>
>  product - is a stand alone instance or One product. Why Would it ever
> have the multiplied price with ''quantity'' ?.
>
>
> I remember many years ago I read the beginner''s book "Agile
Web
> Development with Rails", is that example from it? I think you missed
> something.thank very much for the effort yes this is from the book agile web
development with rails sorry about it im just starting to learn ruby on
rails

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ruby LED

2012-Feb-21 15:53 UTC

head link

Re: nil can''t be coerced into BigDecimal

>
>>> PS. Why are you writing product.price=?
>> i belive it is same with product.price * quantity
>> to show the sum of all products inside my cart
>
> Logic, logic, logic.
>
>  product - is a stand alone instance or One product. Why Would it ever
> have the multiplied price with ''quantity'' ?.
>
>
> I remember many years ago I read the beginner''s book "Agile
Web
> Development with Rails", is that example from it? I think you missed
> something.thank very much for the effort yes this is from the book agile web
development with rails sorry about it im just starting to learn ruby on
rails, uhm i didnt miss anything its just other snippets in the book is 
not properly working :(

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Rails - Feb 2012 - nil can't be coerced into BigDecimal

nil can''t be coerced into BigDecimal

Re: nil can''t be coerced into BigDecimal

Re: nil can''t be coerced into BigDecimal

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