Question

从代码in this Answer开始，我有一个快速工作的东西，它解析yaml文件中的待办事项任务项列表。

但如果我添加第二个文档：Data.Yaml.decode不再解码任何内容，只返回Nothing。

像这样：

---
-   name: >
        this is a test task
    state: finished

-   name: >
        this is a second test task
    state: todo
---
-   name: noname
    state: nostate

所以我想知道在使用Data.Yaml解析时是否可以使用Yaml的文档功能？

或者我做错了什么？

这是代码：

{-# LANGUAGE OverloadedStrings #-}
import Data.Yaml
import Control.Applicative -- <$>, <*>
import Data.Maybe (fromJust)

import qualified Data.ByteString.Char8 as BS

data Task = Task {    name :: String,
                      state :: String }
                      deriving (Show)

instance FromJSON Task where
    parseJSON (Object v) = Task <$>
                           v .: "name" <*>
                           v .: "state"
    -- A non-Object value is of the wrong type, so fail.
    parseJSON _ = error "Can't parse Task from YAML/JSON"

main = do
         ymlData <- BS.readFile "/tmp/test2.yaml"
         let users = Data.Yaml.decode ymlData :: Maybe [Task]
         -- Print it, just for show
         print $ fromJust users

Answer 1

您需要...来分隔文档，例如：

---
-   name: >
        this is a test task
    state: finished

-   name: >
        this is a second test task
    state: todo
...
---
-   name: noname
    state: nostate

使用Data.Yaml在一个文件中解析几个Yaml文档

1 个答案: