Rails - Dec 2006 - Navigating model relationships

i''m trying to understand navigating activerecord relationships. For
example I''ve got:

class Product < ActiveRecord::Base
  has_many :line_items
end
class LineItem < ActiveRecord::Base
  belongs_to :product
  has_one :price
end
class Price < ActiveRecord::Base
  belongs_to :line_item
end

ok so Price isn''t the best example but the point is LineItem has_one
Price.
so I''ve passed a Product object from the controller into a view and
i''m
iterating over it like thus:

<% for lineitem in @product.line_items %>

then I want to write a conditional statement to test if there''s a price
object for that lineitem so:

<% if lineitem.price %>
  print something
<% end %>

the problem is the "if" line raises:

(eval):1:in `compute_type'': compile error
(eval):1: parse error, unexpected tINTEGER
Object::1

so what am I doing wrong?

thanks


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creativetags wrote:
> i''m trying to understand navigating activerecord relationships.
For
> example I''ve got:
> 
> class Product < ActiveRecord::Base
>   has_many :line_items
> end
> class LineItem < ActiveRecord::Base
>   belongs_to :product
>   has_one :price
> end
> class Price < ActiveRecord::Base
>   belongs_to :line_item
> end
> 
> ok so Price isn''t the best example but the point is LineItem
has_one
> Price.
> so I''ve passed a Product object from the controller into a view
and i''m
> iterating over it like thus:
> 
> <% for lineitem in @product.line_items %>
> 
> then I want to write a conditional statement to test if there''s a
price
> object for that lineitem so:
> 
> <% if lineitem.price %>
>   print something
> <% end %>
> 
> the problem is the "if" line raises:
> 
> (eval):1:in `compute_type'': compile error
> (eval):1: parse error, unexpected tINTEGER
> Object::1
> 
> so what am I doing wrong?
> 
> thanks
I suspect it''s because ''price'' isn''t a
boolean.  Perhaps

unles lineitem.price.nil?

unless lineitem.price.blank?

Alan

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> I suspect it''s because ''price'' isn''t a
boolean. Perhaps
>
> unless lineitem.price.nil?
>
> unless lineitem.price.blank?
sorry still giving the same error.

mark


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your logic seems right as the only things that will return false are the
boolean false and nil.

You may want to check to make sure that you have the correct columns in your
database.  the table prices should have line_item_id and line_items should
contain product_id.  But even that probably wouldn''t return the error
that
you''re receiving.

Other than that all I can think of is to check the rest of your code leading
to that line.

On 12/20/06, creativetags
<creativetags-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
>
> > I suspect it''s because ''price''
isn''t a boolean. Perhaps
> >
> > unless lineitem.price.nil?
> >
> > unless lineitem.price.blank?
>
> sorry still giving the same error.
>
> mark
>
>
> >
>

-- 
Mike Weber
Web Developer
UW-Eau Claire

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ok i just checked all the code - the db seems to be setup correctly
with foreign keys.

I tested the original ''if'' statement i proposed and the
condition
returns false (or nil) skipping the block if there is no price object
associated with the lineitem in the db. I still get the error about
unexpected tINTEGER if there is an associated price.

Anyone know what that means? what it should be?

thanks


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Hi --

On Wed, 20 Dec 2006, Alan Francis wrote:
>
> creativetags wrote:
>> i''m trying to understand navigating activerecord
relationships. For
>> example I''ve got:
>> 
>> class Product < ActiveRecord::Base
>>   has_many :line_items
>> end
>> class LineItem < ActiveRecord::Base
>>   belongs_to :product
>>   has_one :price
>> end
>> class Price < ActiveRecord::Base
>>   belongs_to :line_item
>> end
>> 
>> ok so Price isn''t the best example but the point is LineItem
has_one
>> Price.
>> so I''ve passed a Product object from the controller into a
view and i''m
>> iterating over it like thus:
>> 
>> <% for lineitem in @product.line_items %>
>> 
>> then I want to write a conditional statement to test if
there''s a price
>> object for that lineitem so:
>> 
>> <% if lineitem.price %>
>>   print something
>> <% end %>
>> 
>> the problem is the "if" line raises:
>> 
>> (eval):1:in `compute_type'': compile error
>> (eval):1: parse error, unexpected tINTEGER
>> Object::1
>> 
>> so what am I doing wrong?
>> 
>> thanks
>
> I suspect it''s because ''price'' isn''t a
boolean.  Perhaps
>
> unles lineitem.price.nil?
>
> unless lineitem.price.blank?
That shouldn''t matter; every Ruby expression has a boolean value of
true or false, for purposes of conditional evaluation.


David

-- 
Q. What''s a good holiday present for the serious Rails developer?
A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
    aka The Ruby book for Rails developers!
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)

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Hi --

On Wed, 20 Dec 2006, creativetags wrote:
>
> i''m trying to understand navigating activerecord relationships.
For
> example I''ve got:
>
> class Product < ActiveRecord::Base
> has_many :line_items
> end
> class LineItem < ActiveRecord::Base
> belongs_to :product
> has_one :price
> end
> class Price < ActiveRecord::Base
> belongs_to :line_item
> end
>
> ok so Price isn''t the best example but the point is LineItem
has_one
> Price.
> so I''ve passed a Product object from the controller into a view
and i''m
> iterating over it like thus:
>
> <% for lineitem in @product.line_items %>
>
> then I want to write a conditional statement to test if there''s a
price
> object for that lineitem so:
>
> <% if lineitem.price %>
> print something
> <% end %>
>
> the problem is the "if" line raises:
>
> (eval):1:in `compute_type'': compile error
> (eval):1: parse error, unexpected tINTEGER
> Object::1
>
> so what am I doing wrong?
Do you have an <% end %> for the "for" loop as well as the
"if"?


David

-- 
Q. What''s a good holiday present for the serious Rails developer?
A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
    aka The Ruby book for Rails developers!
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)

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> Do you have an <% end %> for the "for" loop as well as the
"if"?
yeah sorry didn''t include it up there for speed. thanks anyway.


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did you set up the database using migrations or sql statements?  it almost
seems like a type mismatch: it''s getting an integer when it''s
expecting a
float for example.

On 12/20/06, creativetags
<creativetags-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
>
>
> > Do you have an <% end %> for the "for" loop as well as
the "if"?
>
> yeah sorry didn''t include it up there for speed. thanks anyway.
>
>
> >
>

-- 
Mike Weber
Web Developer
UW-Eau Claire

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i set up the db with migrations. i can''t see any wrong types in the db
schema that I know of.

It''s strange because it''s not actually returning an integer to
lineitem.price it''s throwing an error saying it''s returning an
integer.
Is it saying that because it''s expecting a boolean for the
''if''
condition? If so how do I write a condition to test if a lineitem has a
price?


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>From what you described, the error is a compile error and has nothing
to do with object type at runtime. I would double check your source
code to make sure you don''t have an integer on that line somewhere
(like a 1 for the letter i). If your still having a problem post the
exact source code and someone will be able to figure it out.

-Paul


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i think i''m getting somewhere now - ''type'' appears to
be reserved for
single table inheritance. the things you don''t think of when
you''re a
newbie :)

thanks again for all your help


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It seems that "type" is a forbidden column name in Ruby''s
ActiveRecord.

More details here:
http://nhw.pl/wp/2006/05/26/column-names-restrictions/

Hope that helps.

--Stephen

-- 
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