小编Lau*_*oki的帖子

我是Haskell的新手,我试着理解如何正确地执行IO.

以下工作正常:

main = do
  action <- cmdParser
  putStrLn "Username to add to the password manager:"
  username <- getLine
  case action of
    Add -> persist entry
      where
        entry = Entry username "somepassword"

以下结果导致编译错误:

main = do
  action <- cmdParser
  case action of
    Add -> persist entry
      where
        entry = Entry promptUsername "somepassword"

promptUsername = do
  putStrLn "Username to add to the password manager:"
  username <- getLine

错误在这里:

Couldn't match expected type `IO b0' with actual type `[Char]'
Expected type: IO …

我想观察 iOS 键盘的高度。我如何使用 RxSwift 做到这一点？