F#尝试处理未处理的异常 [英] F# try with unhandled exceptions

问题描述

在下面的代码中，我想读取一个文件并返回所有行；如果出现IO错误，我希望程序退出并显示错误消息到控制台.但是程序仍然会遇到未处理的异常.最佳做法是什么? (我想我不需要Some/None，因为无论如何我都想退出程序.)谢谢.

In the following code, I want to read a file and return all lines; if there is IO error, I want the program exit with error message print to console. But the program still run into unhandled exception. What's the best practice for this? (I guess I dont need Some/None since I want to the program exit at error anyway.) thanks.

let lines = 
    try 
      IO.File.ReadAllLines("test.txt")
    with
    | ex -> failwithf " %s" ex.Message

推荐答案

您可以键入测试模式匹配.

You can do type test pattern matching.

let lines = 
    try 
      IO.File.ReadAllLines("test.txt")
    with
    | :? System.IO.IOException as e ->
        printfn " %s" e.Message
        // This will terminate the program
        System.Environment.Exit e.HResult
        // We have to yield control or return a string array
        Array.empty
    | ex -> failwithf " %s" ex.Message

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