Insert key/value pair into hash, then read it out

rubyonrails-talk
1

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:

2

... anybody ... ?

3

@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

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

4

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?

5

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.

6

Great, thanks a lot!