Sinatra App Not Using Erb in Links

Question

The problem I'm having is that Sinatra apps don't always seem to show my ERB when it is used in some specific context of hyperlinks. I have no idea how much is relevant to show for this question, so I'll do the best I can .Basically, I have a file in my Sinatra app called book_show.erb. It has the following line:

<p><a href="/books/#{@book.id}/edit">Edit Book</a></p>

However, when that link is rendered in the browser, it links like this:

http://localhost:9292/books/#{@book.id}/edit

The #{@book.id} was not replaced with the actual ID value. There is a @book object and I do use it in other contexts in that very same file. For example:

<h1><%= @book.series %></h2>
<h2><%= @book.title %></h2>

<h3>Timeframe:</h3>
<p><%= @book.timeframe %></p>

I don't even know if my routes would make a difference here for diagnosing this but all of the relevant routes for my books functionality are:

get '/books' do
  @title = 'Book Database'
  @books = Book.all
  erb :books
end

get '/books/new' do
  @book = Book.new
  erb :book_add
end

get '/books/:id' do
  @book = Book.get(params[:id])
  erb :book_show
end

post '/books' do
  book = Book.create(params[:book])
  redirect to("/books/#{book.id}")
end

I don't know what else to show to help diagnose this problem. I'm hoping someone sees something terribly obvious that I'm missing.

Adding a book to the database works just fine; it's only that edit link that I can't get to work correctly -- and that would seem to be pure HTML/ERB. In order to test it, I also added this line to the page:

<p>Testing: <%= "/books/#{@book.id}/edit" %>

That came back and returned this text:

Testing: /books/4/edit

So I know the ID is getting stored. It has to be something to do with the hyperlink but I can find nothing useful on Sinatra that helps at all with this.

Answer 1

ERB template does not behave like a ruby string - you need to explicitly tell it you exit the 'template' part into the 'logic' part. It looks very odd when it comes to attributes:

<p><a href="/books/<%= @book.id %>/edit">Edit Book</a></p>

You could use link_to helpers to make it look better:

link_to('Edit Book', controller: 'books', action: 'edit', id: @book.id)