Class | ActiveSupport::Cache::Store |
In: |
vendor/rails/activesupport/lib/active_support/cache.rb
|
Parent: | Object |
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 vendor/rails/activesupport/lib/active_support/cache.rb, line 202 202: def decrement(key, amount = 1) 203: log("decrementing", key, amount) 204: if num = read(key) 205: write(key, num - amount) 206: else 207: nil 208: end 209: end
# File vendor/rails/activesupport/lib/active_support/cache.rb, line 181 181: def delete(key, options = nil) 182: log("delete", key, options) 183: end
# File vendor/rails/activesupport/lib/active_support/cache.rb, line 185 185: def delete_matched(matcher, options = nil) 186: log("delete matched", matcher.inspect, options) 187: end
# File vendor/rails/activesupport/lib/active_support/cache.rb, line 189 189: def exist?(key, options = nil) 190: log("exist?", key, options) 191: 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 vendor/rails/activesupport/lib/active_support/cache.rb, line 128 128: def fetch(key, options = {}) 129: @logger_off = true 130: if !options[:force] && value = read(key, options) 131: @logger_off = false 132: log("hit", key, options) 133: value 134: elsif block_given? 135: @logger_off = false 136: log("miss", key, options) 137: 138: value = nil 139: seconds = Benchmark.realtime { value = yield } 140: 141: @logger_off = true 142: write(key, value, options) 143: @logger_off = false 144: 145: log("write (will save #{'%.2f' % (seconds * 1000)}ms)", key, nil) 146: 147: value 148: end 149: end
# File vendor/rails/activesupport/lib/active_support/cache.rb, line 193 193: def increment(key, amount = 1) 194: log("incrementing", key, amount) 195: if num = read(key) 196: write(key, num + amount) 197: else 198: nil 199: end 200: 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 vendor/rails/activesupport/lib/active_support/cache.rb, line 158 158: def read(key, options = nil) 159: log("read", key, options) 160: end
# File vendor/rails/activesupport/lib/active_support/cache.rb, line 83 83: def silence! 84: @silence = true 85: self 86: 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 vendor/rails/activesupport/lib/active_support/cache.rb, line 177 177: def write(key, value, options = nil) 178: log("write", key, options) 179: end