An abstract cache store class. There are multiple cache store implementations, each having its own additional features. See the classes under the ActiveSupport::Cache module, e.g. ActiveSupport::Cache::MemCacheStore. MemCacheStore is currently the most popular cache store for large production websites.
ActiveSupport::Cache::Store is meant for caching strings. Some cache store implementations, like MemoryStore, are able to cache arbitrary Ruby objects, but don't count on every cache store to be able to do that.
cache = ActiveSupport::Cache::MemoryStore.new cache.read("city") # => nil cache.write("city", "Duckburgh") cache.read("city") # => "Duckburgh"
# File lib/active_support/cache.rb, line 225 def decrement(key, amount = 1) log("decrementing", key, amount) if num = read(key) write(key, num - amount) else nil end end
# File lib/active_support/cache.rb, line 204 def delete(key, options = nil) log("delete", key, options) end
# File lib/active_support/cache.rb, line 208 def delete_matched(matcher, options = nil) log("delete matched", matcher.inspect, options) end
# File lib/active_support/cache.rb, line 212 def exist?(key, options = nil) log("exist?", key, options) end
Fetches data from the cache, using the given key. If there is data in the cache with the given key, then that data is returned.
If there is no such data in the cache (a cache miss occurred), then then nil will be returned. However, if a block has been passed, then that block will be run in the event of a cache miss. The return value of the block will be written to the cache under the given cache key, and that return value will be returned.
cache.write("today", "Monday") cache.fetch("today") # => "Monday" cache.fetch("city") # => nil cache.fetch("city") do "Duckburgh" end cache.fetch("city") # => "Duckburgh"
You may also specify additional options via the options argument. Setting :force => true will force a cache miss:
cache.write("today", "Monday") cache.fetch("today", :force => true) # => nil
Other options will be handled by the specific cache store implementation. Internally, fetch calls read, and calls write on a cache miss. options will be passed to the read and write calls.
For example, MemCacheStore's write method supports the :expires_in option, which tells the memcached server to automatically expire the cache item after a certain period. We can use this option with fetch too:
cache = ActiveSupport::Cache::MemCacheStore.new cache.fetch("foo", :force => true, :expires_in => 5.seconds) do "bar" end cache.fetch("foo") # => "bar" sleep(6) cache.fetch("foo") # => nil
# File lib/active_support/cache.rb, line 151 def fetch(key, options = {}) @logger_off = true if !options[:force] && value = read(key, options) @logger_off = false log("hit", key, options) value elsif block_given? @logger_off = false log("miss", key, options) value = nil ms = Benchmark.ms { value = yield } @logger_off = true write(key, value, options) @logger_off = false log('write (will save %.2fms)' % ms, key, nil) value end end
# File lib/active_support/cache.rb, line 216 def increment(key, amount = 1) log("incrementing", key, amount) if num = read(key) write(key, num + amount) else nil end end
# File lib/active_support/cache.rb, line 104 def mute previous_silence, @silence = defined?(@silence) && @silence, true yield ensure @silence = previous_silence end
Fetches data from the cache, using the given key. If there is data in the cache with the given key, then that data is returned. Otherwise, nil is returned.
You may also specify additional options via the options argument. The specific cache store implementation will decide what to do with options.
# File lib/active_support/cache.rb, line 181 def read(key, options = nil) log("read", key, options) end
# File lib/active_support/cache.rb, line 96 def silence! @silence = true self end
Writes the given value to the cache, with the given key.
You may also specify additional options via the options argument. The specific cache store implementation will decide what to do with options.
For example, MemCacheStore supports the :expires_in option, which tells the memcached server to automatically expire the cache item after a certain period:
cache = ActiveSupport::Cache::MemCacheStore.new cache.write("foo", "bar", :expires_in => 5.seconds) cache.read("foo") # => "bar" sleep(6) cache.read("foo") # => nil
# File lib/active_support/cache.rb, line 200 def write(key, value, options = nil) log("write", key, options) end
Generated with the Darkfish Rdoc Generator 2.