Question

我是F＃的新手，很抱歉，如果这看起来太愚蠢了。我试图通过FileSystemWatcher收听文件创建和删除事件。现在我想创建一个观察程序，根据目录中添加和删除的文件显示更改计数。因此，无论何时将文件添加到目录中，计数都会增加1，而当文件被删除时减少。我的代码如下：

let watcher = new FileSystemWatcher(@".")
watcher.EnableRaisingEvents <- true

let created = watcher.Created

let deleted = watcher.Deleted

type Change =
  | Addition of string
  | Removal  of string

let a = created |> Observable.map (fun eventArgs ->
  Addition eventArgs.Name)

let r = deleted |> Observable.map (fun eventArgs ->
  Removal eventArgs.Name)

let changes = Observable.merge a r

let collector count state =
    match state with
    | Addition x           -> count + 1
    | Removal x            -> count - 1

let createdCount =
    changes |> Observable.scan (fun count s -> collector count s) 0

但它在Observable.scan上发出以下错误：

This expression was expected to have type
    FSI_0024.Change    
but here has type
    FSI_0017.Change

类型相同，但我不理解这个FSI_xxxx部分。可能是什么问题？

Answer 1

当编译器使用相同类型的旧版本时会导致此类错误。

最简单的解决方案是重启FSI会话

该表达式的类型为FSI_0024.xxx，但此处的类型为FSI_0017.xxx

1 个答案: