Rails 3.1: Determine if asset exists

问题

Is there a built-in way to determine if an asset exists without resorting to File.exists?(File.join(Rails.root, "foo", "bar", "baz")) and that looks through the asset paths.

My app goes and fetches images from a remote server on a Resque queue; until we have the image downloaded I want to serve a placeholder image. Currently I'm using File.exists... but this means hard-coding a path, which sucks, or looking through the configured asset paths. It seems like this should be there already, but I can't find it in the docs.

回答1:

Given an image in app/assets/images/lolshirts/theme/bg-header.png,

Rails.application.assets.find_asset 'lolshirts/theme/bg-header.png'
 => #> Sprockets::StaticAsset:0x80c388ec pathname="/Users/joevandyk/projects/tanga/sites/lolshirts/app/assets/images/lolshirts/theme/bg-header.png", mtime=2011-10-07 12:34:48 -0700, digest="a63cc84aca38e2172ae25de3d837c71a">

Rails.application.assets.find_asset 'notthere.png'
 => nil

回答2:

Since this is still the top question when searching Google, and since the accepted answer does not work properly in production (at least in some cases), here is the solution that works for me (Rails 4.2.5.1):

def asset_exist?(path)
  if Rails.configuration.assets.compile
    Rails.application.precompiled_assets.include? path
  else
    Rails.application.assets_manifest.assets[path].present?
  end
end

This is copied from this github issue

回答3:

See this answer: https://stackoverflow.com/a/8217598/549252

= Rails.application.assets.find_asset("my_asset.css").nil?

回答4:

Please see the answer here for a discussion on why find_asset may not always work:

Include Assets Only If They Exist

来源：https://stackoverflow.com/questions/6782978/rails-3-1-determine-if-asset-exists

标签

ruby-on-rails-3.1

asset-pipeline