Rails - Nov 2008 - Insert key/value pair into hash, then read it out

Hi there,

I''ve been trying to figure out if/how the following is possible...

@books: array of books

@books.each do |book|
  do stuff...
  do stuff...
  do stuff...
  book["number_of_pages"] = 123   #this is supposed to
"inject" the
key/value pair
end

I want to:
=========
-> "inject" the key ''number_of_pages'' with the
value ''123'' into the hash
"book" ("book" IS a hash, right?), for every book in @books

-> Then, show in the view: All "Number of pages":  <%=
@books.collect
{|b| [b.number_of_pages] } %>

It doesn''t work like this... (-> "undefined method
`number_of_pages'' for
#<Book:0xb5c022bc>")

How can I solve it...?

Many thanks for your help!
Tom
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... anybody ... ?
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On Fri, Nov 7, 2008 at 7:28 AM, Tom Ha
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>wrote:
> @books: array of books
>  @books.each do |book|
>  do stuff...
>  do stuff...
>  do stuff...
>  book["number_of_pages"] = 123   #this is supposed to
"inject" the
> key/value pair
> end


> -> "inject" the key ''number_of_pages'' with
the value ''123'' into the hash
> "book" ("book" IS a hash, right?), for every book in
@books

No, book is a class, I assume at least.

Probably in your models directory you have a book.rb file that has

class Book < ActiveRecord::Base
<stuff>
end

-> Then, show in the view: All "Number of pages":  <%=
@books.collect
> {|b| [b.number_of_pages] } %>
>
> It doesn''t work like this... (-> "undefined method
`number_of_pages'' for
> #<Book:0xb5c022bc>")
>
You probably want a column called number_of_pages in your books table

Then you can do:
book.number_of_pages = 123
book.number_of_pages #=> 123

Hope that helps

Mikel

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Thanks, Mikel. We''re half way there, I guess:
> No, book is a class, I assume at least.
> 
> Probably in your models directory you have a book.rb file that has
> 
> class Book < ActiveRecord::Base
> <stuff>
> end
Yes, that''s the case.
> You probably want a column called number_of_pages in your books table
> 
> Then you can do:
> book.number_of_pages = 123
> book.number_of_pages #=> 123
Not really. Actually, I don''t want to store the
"number_of_pages" in a
database, I''d just lik to add it "on the fly" to each
"book" to be able
to display it in the view, for each "book".

Is this possible in my case?
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On Nov 7, 2008, at 5:48 AM, Tom Ha wrote:
>
> Thanks, Mikel. We''re half way there, I guess:
>
>> No, book is a class, I assume at least.
>>
>> Probably in your models directory you have a book.rb file that has
>>
>> class Book < ActiveRecord::Base
>> <stuff>
>> end
>
> Yes, that''s the case.
>
>> You probably want a column called number_of_pages in your books table
>>
>> Then you can do:
>> book.number_of_pages = 123
>> book.number_of_pages #=> 123
>
> Not really. Actually, I don''t want to store the
"number_of_pages" in a
> database, I''d just lik to add it "on the fly" to each
"book" to be
> able
> to display it in the view, for each "book".
>
> Is this possible in my case?


If you add these to the class:

def calc_number_of_pages
   @page_count = (your code to determine page count)
end

def number_of_pages
   @page_count
end


Then you can do:

@books.each do |book|
  book.calc_number_of_pages
end

Then in your view you can have

<%= book.number_of_pages %>

and it will do what you''ve described.



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Great, thanks a lot!
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