diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/Hakyll/Core/Rules.hs | 21 |
1 files changed, 20 insertions, 1 deletions
diff --git a/src/Hakyll/Core/Rules.hs b/src/Hakyll/Core/Rules.hs index 1aa3ad3..eba3fb9 100644 --- a/src/Hakyll/Core/Rules.hs +++ b/src/Hakyll/Core/Rules.hs @@ -81,7 +81,9 @@ compile pattern compiler = RulesM $ do -- | Add a compilation rule -- -- This sets a compiler for the given identifier. No resource is needed, since --- we are creating the item from scratch. +-- we are creating the item from scratch. This is useful if you want to create a +-- page on your site that just takes content from other items -- but has no +-- actual content itself. -- create :: (Binary a, Typeable a, Writable a) => Identifier -> Compiler () a -> Rules @@ -98,6 +100,23 @@ route pattern route' = tellRoute $ ifMatch pattern route' -- Metacompilers are a special class of compilers: they are compilers which -- produce other compilers. -- +-- This is needed when the list of compilers depends on something we cannot know +-- before actually running other compilers. The most typical example is if we +-- have a blogpost using tags. +-- +-- Every post has a collection of tags. For example, +-- +-- > post1: code, haskell +-- > post2: code, random +-- +-- Now, we want to create a list of posts for every tag. We cannot write this +-- down in our 'Rules' DSL directly, since we don't know what tags the different +-- posts will have -- we depend on information that will only be available when +-- we are actually compiling the pages. +-- +-- The solution is simple, using 'metaCompile', we can add a compiler that will +-- parse the pages and produce the compilers needed for the different tag pages. +-- -- And indeed, we can see that the first argument to 'metaCompile' is a -- 'Compiler' which produces a list of ('Identifier', 'Compiler') pairs. The -- idea is simple: 'metaCompile' produces a list of compilers, and the |