F#:如何指定要使用的静态重载? [英] F#: how to specify static overload to use?

问题描述

我有两个用C#代码声明的类:

I have two classes declared in C# code:

public class A
{
     public static bool TryParse(string value, out A result)
     {
         ...
     }
}

public class B : A
{
     public static bool TryParse(string value, out B result)
     {
         ...
     }
}

从C#调用B.TryParse没问题，因为正确的重载由out参数类型确定，该参数类型应事先声明.由于在F#中将参数转换为结果的一部分，因此我们得到了两个具有相同参数签名的函数...并且从F#进行调用会导致A unique overload for method 'TryParse' could not be determined based on type information prior to this program point. A type annotation may be needed.错误.我了解这个问题，甚至可以将TryParse声明为new ...如果它不是静态的.

While calling B.TryParse from C# isn't problem, because correct overload is determined by out parameter type, which should be declared in advance. As out parameter is transformet to part of result in F#, we got two function with same parameter signature... And call from F# causes A unique overload for method 'TryParse' could not be determined based on type information prior to this program point. A type annotation may be needed. error. I understand the issue, and would even declare TryParse as new... If it weren't static.

消息本身不是很有帮助:绝对不能清除注释类型和添加位置.

The message itself is not very helpful: it's absolutely not cleare what kind of annotation and where to add.

我怎么打这个电话? 最愚蠢的想法是重命名功能之一，但是可能还有更聪明的方法吗?

How can I do this call? Most stupid idea is to rename one of functions, but may be there are more clever way?

推荐答案

您需要在要传递给try方法的变量中添加类型注释，在这种情况下，out变量将改变.我认为类似这样的方法应该起作用:

You need to add a type annotation to the variables you are passing to the try method, in this case the out variable as this is the thing that changes. I think something like this should work:

let res, (b:B) = B.TryParse "MyString"

在F#类型中，注释在标识符之后，并以冒号(:)开头.

In F# type annotations come after the an identifier and are preceded by a colon (:).

(注意:in F#out参数可以从结果中作为元组恢复)

(Note: in F# out parameters can be recovered as tuple from the result)

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