給定一個受成員約束限制的值，我可以作爲第一類函數訪問成員嗎？

Question

是否有可能將約束成員作爲第一類函數（給定對象）？如果是這樣，什麼是正確的語法使用？

// Example: property getter as a first-class function 
    type Test() = 
    member x.Value = "42" 

    let t = Test() 
    let getter = t.get_Value // works as expected 


    // now generically: 
    let inline getGetter< ^a when ^a : (member get_Value : unit -> string)> item = 
    // call getter 
    let value = (^a : (member get_Value : unit -> string) item) 
    // try to get getter as first-class function 
    let getter = item.get_Value // doesn't compile: "Lookup on object of indeterminate type..." 
    () 

Answer 1

我認爲這是你在找什麼：

type Test() = 
    member x.Value = "42" 

    let inline getGetter< ^a when ^a : (member get_Value : unit -> string)> item = 
    fun() -> (^a : (member get_Value : unit -> string) item) 

    let t = Test() 
    let getter = getGetter t 
    let value = getter()