fresh_when

Sets the etag, last_modified, or both on the response and renders a 304 Not Modified response if the request is already fresh.

Parameters:

• :etag.

• :last_modified.

• :public By default the Cache-Control header is private, set this to true if you want your application to be cachable by other devices (proxy caches).

• :template By default, the template digest for the current controller/action is included in ETags. If the action renders a different template, you can include its digest instead. If the action doesn’t render a template at all, you can pass template: false to skip any attempt to check for a template digest.

Example:

def show
  @article = Article.find(params[:id])
  fresh_when(etag: @article, last_modified: @article.created_at, public: true)
end

This will render the show template if the request isn’t sending a matching ETag or If-Modified-Since header and just a 304 Not Modified response if there’s a match.

You can also just pass a record where last_modified will be set by calling updated_at and the etag by passing the object itself.

def show
  @article = Article.find(params[:id])
  fresh_when(@article)
end

When passing a record, you can still set whether the public header:

def show
  @article = Article.find(params[:id])
  fresh_when(@article, public: true)
end

When rendering a different template than the default controller/action style, you can indicate which digest to include in the ETag:

before_action { fresh_when @article, template: 'widgets/show' }