Rails -nokogiri GEM: Detect MIME type of image in URL

Question

I am using gem nokogiri to scrap img tag src values. Sometimes url doesn't show the image file name with extension.

So I am trying to detect the image MIME type as follows:

MIME::Types.type_for("http://web.com/img/12457634").first.content_type # => "image/gif"

But it shows error:

undefined method `content_type' for nil:NilClass (NoMethodError)

Any solution?

Answer 1

You get this error:

undefined method `content_type' for nil:NilClass (NoMethodError)

because the MIME::Types.type_for("http://web.com/img/12457634").first object is nil sometimes.

To avoid this problem, do this:

MIME::Types.type_for("http://web.com/img/12457634").first.try(:content_type)

So, it does not crash your program if it's nil. If it's not nil, you get the correct content_type

Alternatively, to check the Content-Type header for image using Net::HTTP, you can write a method like this:

def valid_image_exists?(url)
    url = URI.parse(url)
    Net::HTTP.start(url.host, url.port) do |http|
      return http.head(url.request_uri)['Content-Type'].start_with? 'image'
    end
end