How to write ruby code in option of image tag?

Question

Today when working with images, I have a problem: when an image is absent or has invalid url (404 or so) I need to replace it with asset_path("default_avatar.png"). So I tried:

def get_url_avatar url
  return url if url.present? && Faraday.head(url).status == 200
  asset_path "default_avatar.png"
end

But then I found other solution - the onerror option in image_tag to handle the problem on the clientside. The new code:

<%= image_tag (user.avatar),
    class: "avatar",
    onerror: "this.src='asset_path("default_avatar.png")';" %>

or

<%= image_tag (user.avatar),
    class: "avatar",
    onerror: "this.src='<%= asset_path("default_avatar.png") %>';" %>

Now I have a new problem with image_tag. I need to get value of asset_path("default_avatar.png") in onerror javascript handler.
But I can't write ruby in onerror handler. How to do it ?

Answer 1

In erb everything between <%= and %> is ruby code, so use ruby string interpolation there:

<%= image_tag (user.avatar),
    class: "avatar",
    onerror: "this.src='#{asset_path("default_avatar.png")}';" %>