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我一直在搞乱 F# 和它的反射，试图从 F# 中动态创建一个记录类型对象，我得到了大部分工作（如下所示）但有一件事 - 我通过反射创建的记录具有类型“ obj” 而不是它应该的那个（“Person”），我似乎无法以任何方式向上转换它。

#light

type Person = {
    Name:string;
    Age:int;
}

let example = {Name = "Fredrik"; Age = 23;}
// example has type Person = {Name = "Fredrik"; Age = 23;}

let creator = Reflection.FSharpValue.PrecomputeRecordConstructor(example.GetType(), 
               System.Reflection.BindingFlags.Public)

let reflected = creator [| ("thr" :> obj); (23 :> obj) |]
// here reflected will have the type obj = {Name = "thr"; Age = 23;}

// Function that changes the name of a Person record
let changeName (x:Person) (name:string) = 
    { x with Name = name }

// Works with "example" which is has type "Person"
changeName example "Johan"

// But not with "reflected" since it has type "obj"
changeName reflected "Jack" // Error "This expression has type obj but is here used with type Person. "

// But casting reflected to Person doesn't work either
(reflected :> Person) // Type constraint mismatch. The type   obj is not compatible with 
                      // type  Person. The type 'obj' is not compatible with the type 'Person'. 
                      // C:\Users\thr\Documents\Visual Studio 2008\Projects\
                      // Reflection\Reflection\Script.fsx   34  2   Reflection
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1 回答 1

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尝试使用 other cast 运算符（因为这次您正在以另一种方式进行投射）

所以 changeName (reflected :?> Person) "Jack"

于 2009-03-12T11:11:07.017 回答