So maybe this has been done before, but this is something I wrote that I
found useful.
Many of the ''fragments'' I wanted to cache differed only by
some small
value like the :id of the :url, but because this changed every request,
the options were to either store a fragment for every :id, or to not
cache.
So I wrote a helper I call ''dynamic_cache''. It works by using
escaped
Erb INSIDE of an ERb fragment, and calling render :inline on the cached
fragment before returning.
So for instance:
<% cache do %>
<%= link_to_remote ''My Link'', :url => { :id =>
@my_id } %>
<% end %>
This doesn''t cache, since the :id is variable.
So with dynamic_cache it would look like the following:
<% dynamic_cache do %>
<%= link_to_remote ''My Link'', :url => { :id =>
''\<\%= @my_id \%\>'' } %>
<% end %>
@my_id doesn''t get evaluated and the escaped ERb delimiters get cleaned
up to just ''<%= @my_id %>''. The cache then calls render
:inline on the
cached fragment which evaluates any of the newly un-escaped ERb with the
current values at the time of the render.
Add the following to your application.rb for this to work....
module ActionController #:nodoc:
module Caching
module Fragments
def dynamic_cache_erb_fragment(block, name = {}, options = nil)
# this grabs the _erbout variable from the blocks scope
buffer = eval(''_erbout'', block.binding)
if ! cache = read_fragment(name, options)
# by default the block.call will write everything to the
_erbout
# this is an ugly way to get around that, and is the same
method used in capture_erb_with_buffer
# but it is only called the first time, so not a big deal
pos = buffer.length
block.call
cache = buffer[pos..-1]
buffer[pos..-1] = ''''
# save it to the cache if we are caching
write_fragment(name, cache, options) if perform_caching
end
buffer.concat(render :inline => cache)
end
end
end
end
module ActionView
module Helpers
module CacheHelper
def dynamic_cache(name = {}, &block)
@controller.dynamic_cache_erb_fragment(block, name)
end
end
end
end
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You can also do some more complicated caching than would otherwise be
allowed (ie, caching larger blocks of code...it gets a little ugly, but
may be useful.
In the following example, condtional is executed at the time of
rendering, while the links are cached.
<% dynamic_cache do %>
<%= ''\<\% if @my_test_value == "HURRAY"
\%\>'' %>
<%= link_to "My Test2", "HURRAY" %>
<%= ''\<\% else \%\>'' %>
<%= link_to "My Test3", "HIDEYHO" %>
<%= ''\<\% end \%\>'' %>
<% end %>
PLEASE NOTE: THERE IS A BUG HERE CURRENTLY I NEED TO FIX. If you use
more than one dynamic_cache request you get the a double render error.
I need to figure out how to get the effect of render :inline with
actually using render.
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OK, here is a fixed version (just added ''@template.'' to the
render :
module ActionController #:nodoc:
module Caching
module Fragments
def dynamic_cache_erb_fragment(block, name = {}, options = nil)
# this grabs the _erbout variable from the blocks scope
buffer = eval(''_erbout'', block.binding)
if ! cache = read_fragment(name, options)
# by default the block.call will write everything to the
_erbout
# this is an ugly way to get around that, and is the same
method used in capture_erb_with_buffer
# but it is only called the first time, so not a big deal
pos = buffer.length
block.call
cache = buffer[pos..-1]
buffer[pos..-1] = ''''
# save it to the cache if we are caching
write_fragment(name, cache, options) if perform_caching
end
logger.error cache
buffer.concat(@template.render(:inline => cache))
end
end
end
end
module ActionView
module Helpers
module CacheHelper
def dynamic_cache(name = {}, &block)
@controller.dynamic_cache_erb_fragment(block, name)
end
end
end
end
Here is a fixed example of conditionals. Notice the use of double
quotes to wrap the escaped ERb.
<% dynamic_cache do %>
<%= "\<\% if @my_test_value == \''BOOOO\''
\%\>" %>
<%= link_to "My Test", "/\<\%= @my_test_value
\%\>" %>
<%= "\<\% else \%\>" %>
<%= link_to "My Test", "/\<\%= @my_test_value
\%\>2" %>
<%= "\<\% end \%\>" %>
<% end %>
Obviously, another option would be to use a separate delimiter and
replace it with ''<%'' and ''%>'' in the
dynamic_cache method when it
initially creates the cache record.
Like,
<% dynamic_cache do %>
<%= "#% if @my_test_value == \''BOOOO\'' %#"
%>
<%= link_to "My Test", "/#%= @my_test_value %#" %>
<%= "#% else \%\>" %#>
<%= link_to "My Test", "/#%= @my_test_value %#>2"
%>
<%= "#% end %#>" %>
<% end %>
You would just need to cache.gsub for ''%#'' and
''#%'' before
write_fragment.
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Sorry, left a logging statement in there, which shouldnt be:
module ActionController #:nodoc:
module Caching
module Fragments
def dynamic_cache_erb_fragment(block, name = {}, options = nil)
# this grabs the _erbout variable from the blocks scope
buffer = eval(''_erbout'', block.binding)
if ! cache = read_fragment(name, options)
# by default the block.call will write everything to the
_erbout
# this is an ugly way to get around that, and is the same
method used in capture_erb_with_buffer
# but it is only called the first time, so not a big deal
pos = buffer.length
block.call
cache = buffer[pos..-1]
buffer[pos..-1] = ''''
# save it to the cache if we are caching
write_fragment(name, cache, options) if perform_caching
end
buffer.concat(@template.render(:inline => cache))
end
end
end
end
module ActionView
module Helpers
module CacheHelper
def dynamic_cache(name = {}, &block)
@controller.dynamic_cache_erb_fragment(block, name)
end
end
end
end
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