0

我正在尝试修改此示例https://github.com/slamdata/purescript-halogen/blob/v0.12.0/examples/deep-peek/src/Main.purs#L58（相关部分复制如下），而是偷看孙子我只想偷看孩子，或者在这种情况下peekList。我还想将插槽类型保留为 peek 函数中的参数peekList。

peek :: forall a. H.ChildF ListSlot ListQueryP a -> H.ParentDSL State (ListStateP g) Query ListQueryP g ListSlot Unit
peek = coproduct peekList peekTicker <<< H.runChildF

peekList :: forall a. ListQuery a -> H.ParentDSL State (ListStateP g) Query ListQueryP g ListSlot Unit
peekList _ =
  -- we're not actually interested in peeking on the list.
  -- instead of defining a function like this, an alternative would be to use
  -- `(const (pure unit))` in place of `peekList` in the `coproduct` function
  pure unit

peekTicker :: forall a. H.ChildF TickSlot TickQuery a -> H.ParentDSL State (ListStateP g) Query ListQueryP g ListSlot Unit
peekTicker (H.ChildF _ (Tick _)) = H.modify (\st -> { count: st.count + 1 })
peekTicker _ = pure unit

我怎样才能在peekList不丢失 slot 参数的情况下真正偷看？

我试过删除H.runChildF：

peek = coproduct peekList (const (pure unit))

然后在 slot 参数中添加回peekList：

peekList :: forall a. H.ChildF ListSlot ListQuery a -> H.ParentDSL State (ListStateP g) Query ListQueryP g ListSlot Unit

但是然后在peek我收到错误“尝试将 ChildF ListSlot 类型与 Coproduct 类型（ChildF ListSlot ListQuery）匹配时无法将类型 ChildF 与 Coproduct 类型匹配”

如果我只是尝试使用peekListo peek，我会收到错误“在尝试将类型 ChildF ListSlot (Coproduct ListQuery (ChildF TickSlot TickQuery)) 与类型 ChildF ListSlot ListQuery 匹配时，无法将类型 Coproduct ListQuery (ChildF TickSlot TickQuery) 与类型 ListQuery 匹配”

任何帮助将不胜感激，谢谢！

4

1 回答 1

0

我仔细查看了这些类型，发现 peekList 的第二个参数是一个 Coproduct 包装，Either其中Left值是我想要查看的列表查询。所以只需对它们进行模式匹配并添加peekList到组件的peek参数中。此外，我必须更改类型签名以使用ListQueryP而不是ListQuery.

  peekList :: forall a. H.ChildF ListSlot ListQueryP a -> H.ParentDSL State (ListStateP g) Query ListQueryP g ListSlot Unit
  peekList (H.ChildF _ (Coproduct queryEi)) =
    case queryEi of
      Left (AddTicker a) -> pure unit
      _ -> pure unit
于 2017-03-30T05:52:47.240 回答