[英]F#: How do I declare and use ByRef semantics on parameters?
I am wraping some SQL Stored Procs with in/out parameters. 我正在使用输入/输出参数包装一些SQL存储过程。 This of course means I have to do ugly stuff like declare my parameters as by reference and use mutables. 这当然意味着我必须做一些丑陋的事情,例如通过引用声明我的参数并使用mutables。
How would I do this in F#? 我怎么在F#中这样做?
F# does indeed have a byref
parameter . F#确实有一个byref
参数 。 Here's an example from the MSDN page: 以下是MSDN页面中的示例:
type Incrementor(z) =
member this.Increment(i : int byref) =
i <- i + z
Mutable variables also exist (though there's an important difference between using ref
and mutable
variables, either of which can be used for many of the same purposes). 可变变量也存在(尽管使用ref
和mutable
变量之间存在重要差异,其中任何一个都可以用于许多相同的目的)。 The MSDN page on this subject is very informative - including a discussion of when to use which keyword/construct. 关于此主题的MSDN页面提供了非常丰富的信息 - 包括讨论何时使用哪个关键字/构造。
Example of reference variables: 参考变量示例:
// Declare a reference.
let refVar = ref 6
// Change the value referred to by the reference.
refVar := 50
Example of mutable variables: 可变变量的示例:
// Declare a reference.
let mutable refVar = 6
// Change the value referred to by the reference.
refVar <- 50
As you can see, the syntax for assignment (as well as retrieval) differs between the two constructs, too. 如您所见,赋值(以及检索)的语法也在两个构造之间不同。
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