At symbol (@) in link_to argument in Rails

Question

everybody. Forgive any mistakes in my English since it's my second language. Also only my second question here.

I'm learning Ruby on Rails and I have a very basic question, but sadly wasn't able to find a specific answer anywhere.

So, all I did is a simple scaffold (rails g scaffold book title author status:integer), nothing more, and I'm studying everything it does. That's all.

The thing is I don't understand why in the index view the "link_to" helper uses "book" as argument instead of "@books" for both Edit and Destroy links.

Since in the show view the same "link_to" uses @book for Edit.

At first, I thought they could be interchangeable, but they aren't, since when I change the "@", Rails throws an error. I'm clearly missing something basic here.

Where does this difference in both views come from?

Thank you all.

Answer 1

In your view show @book is a variable that was declared in your controller and that contains a collection of books. This collection is traversed through the for_each method, on each tour you get a book that is saved in a variable | book | That book is an instance of your @books collection and link_to receives it to build the link.

In your edit view @book is a variable declared in your controller. You may not be clear why that variable is declared within a method invoked with a before action.

the @ is used to define an @instance_variable