I’m working on using Rails as an API for an iOS mobile app. Swift’s URLRequest supports client side caching protocols which is great, and can work beautifully with Rails if you can send the Cache-Control headers. Here’s how I got it to work.

In Rails:

You need to disable mini-profiler by commenting it out in your Gemfile. Unfortunately it will overwrite your headers, and I did not see how I could turn it off.

# gem 'rack-mini-profiler', '~> 2.0'

In your controller action, add expires_in(time_in_seconds)

  def index
    @recommendations = Treasure.recommendations(@credential.user)
    @result = { records: @recommendations, offset: "" }
    respond_to do |format|
      format.json { render json: @result }
    end
    expires_in 10.minutes
  end

In Swift:

You can now just use the .useProtocolCachePolicy and it will use the Cache-Control directive information to control the cache.

var request: URLRequest

// setup method, endpoint, params etc

// Cache
if useCache {
  request.cachePolicy = .useProtocolCachePolicy
}

Helpful Articles:

• BigBinary on how to enable caching in development
• Helpful HoneyBadger article describing caching including the Cache-Control terms
• Rails Guide on Caching - in general be cautious with client side caching (and caching in general, it is hard to get just right
• Heroku advocates a CDN which needs cache control - they talk about it here