Mathieu questions

• How to display associated model's attribute in Active Admin index with belongs_to/has_many relationship (Rails 3.2/Active Admin)
• rspec - PG::UnableToSend:server closed the connection unexpectedly This probably means the server terminated abnormally
• NoMethodError: undefined method `email' for nil:NilClass : can't send email with devise/sendgrid(Rails 3.2)
• Ruby on Rails 4.2 Asset pipeline not minifying/compressing the application-fingerprinted.js JS file
• Advisory locks or NOWAIT to avoid waiting for locked rows?
• Rspec/capybara - test presence of a class OR another class
• Detect if ios11 device is in low power mode to prevent bad UX on normally correctly autoplaying video
• Prevent huge amount of xhr/ajax calls on Facebook embed iframe
• How should I use Rails to index and query a join table?
• Query an array of json with Active Record (Rails 4/postgresql9.4)

Mathieu answers