Add the rails low level caching post

_drafts/using_rails_low_level_caching.md → _posts/2015-04-02-using_rails_low_level_caching.md

@@ -2,6 +2,7 @@
 title: Using rails low level caching
 layout: post
 ident: using-rails-low-level-caching
+published: true
 ---
 Some times we find our selves having a time expensive method or in some cases
 using an API that costs money per request, or a slow one, I had that issue once
@@ -20,31 +21,36 @@ with `write`
 `write` takes two arguments, a cache key ( the key we're going to use to
 retrieve the data ) and a cache value ( the data that's going to be stored ),
 here's a simple example
-
-    Rails.cache.write 'my_caching_key', some_data
+{% gist e382b9d3fdda2e90c5ab basic_write.rb %}
 Now this data is cached and can be retrieved when needed, there's also extra
 options that can be passed such as expiry period
-
-    Rails.cache.write 'my_caching_key', some_data, expires_in: 1.hour
+{% gist e382b9d3fdda2e90c5ab write_with_expire.rb %}
 When the cache expires it will return nil when accessed.
 
 The caching key could also be an object, not necessarily a string, for example
 the key could be an object, or an array, or a hash, for example
-
-    Rails.cache.write(['some_data', @user], some_data)
-    Rails.cache.write({key: 'important_data', owner: @user}, some_data)
+{% gist e382b9d3fdda2e90c5ab write_with_compund_key.rb %}
 You get the idea.
 
 ##Read
 `read` only takes the cache key to retrieve the data, if the data doesn't exist,
 `nil` will be returned instead
-
-    Rails.cache.read 'my_caching_key'
+{% gist e382b9d3fdda2e90c5ab basic_read.rb %}
 Also like `write`, you can use the non scalar key type to retrieve the data you
 saved in the same way
-
-    Rails.cache.read({key: 'important_data', owner: @user})
+{% gist e382b9d3fdda2e90c5ab read_with_compund_key.rb %}
 
 ##Fetch
+`fetch` is a little special, because it does both `read` and `write`, when the
+cache exists it returns it, but if it isn't it evaluates the block it's given
+then writes the result to the cache and returns the value at the same time, if
+the block isn't expensive ( in terms of time ) you could do with only fetch.
+{% gist e382b9d3fdda2e90c5ab fetch_with_block.rb %}
+If `some_key` is present and not stale, it's returned instantly from the cache,
+if it is, the block is evaluated ( `some_calculations` ) and the return value
+from the block is saved in the `some_key`
+
+Of course as you can see all options mentioned before are also applicable on the
+`fetch` method
 
 [rails-low-level-caching-url]: http://guides.rubyonrails.org/caching_with_rails.html#low-level-caching