f# - 我的匹配看起来很笨重，有没有更好的方法来编码？

Question

这似乎有效，但看起来很笨重。有没有更好的方法来编码？

// Hunting for the best index to use for a data compare
let getIndex connDB strTable =
    match getIndexByPrimaryKey connDB strTable with
    | Some(name) -> Some(name)  
    | None ->
    match getIndexByCluster connDB strTable with
    | Some(name) -> Some(name)
    | None -> 
    match getIndexByFirstColumns connDB strTable with
    | Some(name) -> Some(name)
    | None -> 
    match getIndexByOnlyUnique connDB strTable with
    | Some(name) -> Some(name)
    | None -> 
    match getAnyUniqueIndex connDB strTable with
    | Some(name) -> Some(name)
    | None -> None

Answer 1

可能最简洁的版本是使用 List.tryPick :

let getIndex connDB strTable =
  [ getIndexByPrimaryKey;
    getIndexByCluster;
    getIndexByFirstColumns;
    getIndexByOnlyUnique;
    getAnyUniqueIndex; ]
  |> List.tryPick (fun fn -> fn connDB strTable)

更新:

该技术可以很容易地扩展到使用闭包，因此它适用于具有不同参数的函数(还有很多 fun s :-)):

let getIndex connDB strTable =
  [ fun () -> getIndexByPrimaryKey connDB strTable;
    fun () -> getIndexByCluster connDB strTable;
    fun () -> getIndexByFirstColumns connDB strTable;
    fun () -> getIndexByOnlyUnique connDB strTable;
    fun () -> getAnyUniqueIndex connDB strTable; ]
  |> List.tryPick (fun fn -> fn())