如何将其变为Setter？

Question

setOwner :: File -> User -> File
setOwner f o = f & ownerID .~ (o ^. User.uid)

如何将其转换为Setter？

我无法将它变成镜头，因为getUser :: UserID -> IO User是一种不纯的功能。

Answer 1

我刚刚意识到我之前的回答是错误的。糟糕！

你走了：

ownerS :: Setter File File () User
ownerS = sets (\f file -> setOwner file (f ()))