Question

Why doesn’t this work?

:javascript
    -[1,2,3].each do |number|
        $("#form_#{number}").my_method();

Rails gives me an error, saying that the variable number isn’t defined.

Answer 1

The content of a filter isn’t interpreted as Haml. You can use #{...} for interpolation though, and that’s why you’re seeing the error – the filter sees the #{number} in "#form_#{number}", but the line above where number is defined is simply passed through as it is, not treated as Ruby, so as far as Ruby is concerned number is still undefined.

In this case you could do something like:

:javascript
    #{[1,2,3].map do |number|
        "$(\"#form_#{number}\").my_method();"
    end.join("\n")}

although that’s a bit unwieldy.

A clearer solution might be to create a helper method to create the javascript, which you could call from the filter:

def create_js(arr)
  arr.map do |number|
      "$(\"#form_#{number}\").my_method();"
  end.join("\n")
end

and the Haml would be

:javascript
    #{create_js([1,2,3])}