在正常程序的执行过程中可能会发生异常。
如果我知道它并且只想忽略它 - 我如何在 F# 中实现这一点?
这是我的代码,编译时发出警告:
let sha = new SHA1CryptoServiceProvider()
let maxLength = 10000
let fileSign file =
let fs = File.OpenRead(file)
let mutable res = (0L, [|0uy|])
try
let flLen = fs.Length
let len = int (min (int64 maxLength) flLen)
// read 'len' bytes
let mutable pos = 0
while (pos < len) do
let chunk = fs.Read(buf, pos, len - pos)
pos <- pos + chunk
// get signature
let sign = sha.ComputeHash(buf, 0, len)
// store new result
res <- (flLen, sign)
with
| :? IOException as e -> e |> ignore
finally
if (fs <> null) then
fs.Dispose()
res
警告是:
error FS0010: Unexpected keyword 'finally' in binding. Expected incomplete structured construct at or before this point or other token.
我想要的相应 C# 等效项是:
FileStream fs = null;
try
{
fs = File.OpenRead(file);
// ... other stuff
}
catch
{
// I just do not specify anything
}
finally
{
if (fs != null)
fs.Dispose()
}
如果我只是省略
with
F# 中的块,异常不会被忽略。
最佳答案
try-with 和 try-finally 在 F# 中是单独的构造,因此您需要额外的“尝试”来匹配 finally:
try
try
...
with e -> ...
finally
...
正如 Vitaliy 指出的那样,将“use”用于 finally-that-dispose 更为惯用
use x = some-IDisposable-expr
...
也可以看看
关于“使用”的文档:http://msdn.microsoft.com/en-us/library/dd233240(VS.100).aspx
“使用”的规范:http://research.microsoft.com/en-us/um/cambridge/projects/fsharp/manual/spec.html#_Toc245030850
关于exception-handling - 如何忽略 F# 中的异常,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1789682/