Skip to main content

custom_pdf_page_count_analyzer

🛠️ Building a Custom PDF Page Count Analyzer​

Extend Active Storage with a bespoke analyzer to extract PDF metadata, such as page counts or embedded fonts, and store it in your blob’s metadata for querying or UI display.

  1. Create the analyzer under app/analyzers:
# app/analyzers/active_storage/analyzer/pdf_page_count_analyzer.rb
require 'pdf-reader'

class ActiveStorage::Analyzer::PdfPageCountAnalyzer < ActiveStorage::Analyzer::Base
  def metadata
    reader = PDF::Reader.new(file.download)
    { page_count: reader.page_count }
  rescue => e
    logger.error "Failed to analyze PDF: #{e}";
    {}
  end
end
  1. Register and invoke on attach:
t# config/initializers/active_storage.rb
ActiveStorage::Analyzer.register :pdf, ActiveStorage::Analyzer::PdfPageCountAnalyzer

class Report < ApplicationRecord
  has_one_attached :pdf
  after_commit :extract_page_count, on: :create

  def extract_page_count
    pdf.analyze unless pdf.analyzed?
  end
end

Now report.pdf.metadata[:page_count] holds your custom value.