A module to create cache key using ruby. Often I find myself putting arbitrary strings all over the place in my code base. This module helps as being the 1 place in the code base to define what each key represents

cache_key.rb

module Cache
  # Placeholder for your redis key prefixes
  # Serves as a way to identify which prefix keys belongs to which cache key resource
  #
  # Usage:
  #
  # To create cache key
  #
  # Cache::Key.prefix(Cache::Key::PRESENTER, resource)
  # => "pr:Track:#{track.id}:"
  #
  # Cache::Key.prefix(Cache::Key::PRESENTER, resource, {country: "my"})
  # => "pr:Track:#{track.id}:country:my"
  #
  class Key
    PRESENTER = "pr:".freeze
    VIDEO_URL = "v:url".freeze
    APPS = "a".freeze

    def self.prefix(prefix, resource, *args)
      "#{prefix}#{resource.class.name}:#{resource.id}:#{permutations(args)}"
    end

    def self.simple_prefix(prefix, id)
      "#{prefix}#{id}"
    end

    def self.permutations(args)
      return if args.blank?
      args.map do |a|
        case a
        when Array
          a.join(":")
        when Hash
          a.map{|e| e}.join(":")
        else
          a
        end
      end.join(":")
    end
  end
end

cache_key_spec.rb

# using rspec

describe Cache::Key do
  describe ".prefix" do
    let(:track) { create(:track) }
    let(:video) { create(:video) }

    it "returns a string prefix to use for presenters redis key" do
      str = described_class.prefix(Cache::Key::PRESENTER, track)
      expect(str).to eq "pr:Track:#{track.id}:"
    end

    it "returns a string prefix to use for video url redis key" do
      str = described_class.prefix(Cache::Key::VIDEO_URL, video)
      expect(str).to eq "v:url:Video:#{video.id}:"
    end

    describe "accepts extra arguments to create uniq key" do
      context "when array" do
        it "append map joins elements to string" do
          str = described_class.prefix(Cache::Key::VIDEO_URL, video, [1, 2])
          expect(str).to eq "v:url:Video:#{video.id}:1:2"
        end
      end

      context "when hash" do
        it "append map joins elements to string" do
          str = described_class.prefix(Cache::Key::VIDEO_URL, video, {foo: 'bar', baz: 'foo'})
          expect(str).to eq "v:url:Video:#{video.id}:foo:bar:baz:foo"
        end
      end

      it "append element to string" do
        str = described_class.prefix(Cache::Key::VIDEO_URL, video, "foo")
        expect(str).to eq "v:url:Video:#{video.id}:foo"
      end
    end
  end

  describe ".simple_prefix" do
    it do
      expect(Cache::Key.simple_prefix(Cache::Key::APPS, 1)).to eq "a:1"
    end
  end
end