Heist-0.13的默认AttrSplices是什么？

Question

我正在使用Heist进行一个项目，由于它最近升级到0.13版本，我试用了它，发现原来的HeistConfig改变了很多。

data HeistConfig m = HeistConfig
    { hcInterpretedSplices :: Splices (I.Splice m)
        -- ^ Interpreted splices are the splices that Heist has always had.  They
        -- return a list of nodes and are processed at runtime.
    , hcLoadTimeSplices    :: Splices (I.Splice IO)
        -- ^ Load time splices are like interpreted splices because they return a
        -- list of nodes.  But they are like compiled splices because they are
        -- processed once at load time.  All of Heist's built-in splices should be
        -- used as load time splices.
    , hcCompiledSplices    :: Splices (C.Splice m)
        -- ^ Compiled splices return a DList of Chunks and are processed at load
        -- time to generate a runtime monad action that will be used to render the
        -- template.
    , hcAttributeSplices   :: Splices (AttrSplice m)
        -- ^ Attribute splices are bound to attribute names and return a list of
        -- attributes.
    , hcTemplateLocations  :: [TemplateLocation]
        -- ^ A list of all the locations that Heist should get its templates
    }

所以现在我不能再使用[]作为默认连接，因为有defaultInterpretedSplices和defaultLoadTimeSplices，我发现defaultAttrSplices刚刚错过，那么我应该如何定义它呢？

Answer 1

我认为没有内置的AttrSplices。您应该能够使用mempty、return ()或来自Heist.SpliceAPI的noSplices之一绑定任何剪接。

Splices s是SplicesM s ()的类型别名，它只是一个包装在newtype中的State。Slices s也是Monoid类的实例，所以您可以在这里使用mempty。

newtype SplicesM s a = SplicesM { unSplices :: State (Map Text s) a }
  deriving (Monad, MonadState (Map Text s))

type Splices s = SplicesM s ()

instance Monoid (Splices s) where
  mempty = noSplices
  mappend = unionWithS (\_ b -> b)