README
$Release: 0.1.0 $
About
merb_piece_cache is a Merb plug-in to cache html fragments. You can eliminate database access with this plugin.
Currently only file-base cache store is provided. (Memory-base cache store may be provided in future.)
Install
### install gem
$ sudo gem install merb_helpers_monkey
## add 'dependency "merb_piece_cache"'
$ vi config/dependencies.rb
This plugin requires ‘called_from’ library. If you install this plugin manually, don’t forget to install ‘called_from’.
Example
- controller
-
delay database access by if_not_cached() helper.
- template
-
specify cache area by cache_with() helper.
controller:
def index
## @user is necessary every time
@user = User.current()
## @members is necessary only when cache is refreshed
## (block parameter is called only when cache is expired or not found)
if_not_cached {|cache_key|
@members = Members.all(:order=>[:created_at])
}
render
end
template:
<!-- rendered every time (because never cached) -->
<% if @user %>
Hello <%=h @user %>!
<% else %>
<a href="/login">Login</a>
<% end %>
<!-- rendered only when cache is expired or not found -->
<% lifetime = 5*60 # sec, default is nil(=infinity) %>
<% cache_with("members/index", lifetime) do %>
<ul>
<% for member in @members %>
<li><%=h @member.name %></li>
<% end %>
<ul>
<% end %>
Reference
Merb_piece_cache plugin provides the following helpers.
-
if_not_cached() {|cache_key| … }
Register block as callback object which is called when fragment cache is re-generated (In other words, block parameter is called only when cache is re-generated). Block paramter can receive cache_key as 1st argument so that you can switch data processing according to cache_key.
-
piece_cache(cache_key, lifetime=nil) { … }
When cache is found and not expired, then add cache data into view. Otherwise, call block to re-generate cache data and cache it. (Notice that block parameter is called only when cache is re-generated.) It is able to specify cache lifetime. For example, if you specify lifetime=5*60, cache data will be expired after 5 minutes.
-
cache_with(cache_key, lifetime=nil) { … }
Alias of piece_cache(). You can re-define this helper to extend cache behaviour.
Configuration
You can configure merb_piece_cache plugin in your environment file. (config/environments/production,development,test.rb). For example, add the followings into your ‘development.rb’:
Merb::Plugins.config[:merb_piece_cache] = {
## show cached area in template (convenient for debug!)
:show_area => true,
## directory to place cache files (default: "MERB_ROOT/tmp/cache")
:root_dir => "/var/tmp",
}
Tips
-
You can prepare different data in if_not_exist() according to cache_key.
def index if_not_cached {|cache_key|
case cache_key when /^post/(d+)$/ @post = BlogPost.get($1)
when /^post\/(\d+)/comments$/
@comments = BlogComment.all(:post_id=>$1) end } render
end
-
piece_cache() (and also cache_with()) checks template timestamp. If cache data is older than template timestamp, then cache data will be re-generated.
Author
makoto kuwata <kwa(at)kuwata-lab.com> copyright© 2009 kuwata-lab.com all rights reserved.
License
MIT License