如何在 Go 中表示可选字符串? [英] How do I represent an Optional String in Go?

问题描述

我希望对一个值进行建模，该值可以有两种可能的形式:不存在或字符串.

I wish to model a value which can have two possible forms: absent, or a string.

执行此操作的自然方法是使用 Maybe String、或 Optional、或 string option 等.但是，Go没有这样的变体类型.

The natural way to do this is with Maybe String, or Optional<String>, or string option, etc. However, Go does not have variant types like this.

然后我想，继 Java、C 等之后，替代方案是可空性，或者 Go 中的 nil.但是，nil 不是 Go 中 string 类型的成员.

I then thought, following Java, C, etc., that the alternative would be nullability, or nil in Go. However, nil is not a member of the string type in Go.

搜索，然后我想到使用类型*string.这可以工作，但看起来很尴尬(例如，我不能像获取结构体地址那样获取字符串文字的地址).

Searching, I then thought to use the type *string. This could work, but seems very awkward (e.g. I cannot take the address of the string literal in the same way that I can take the address of a struct literal).

在 Go 中建模这样一个值的惯用方法是什么?

What is the idiomatic way to model such a value in Go?

推荐答案

你可以使用类似 sql.NullString，但我个人会坚持使用 *string.至于尴尬，遗憾的是你不能只是 sp := &"foo" .但是有一个解决方法:

You could use something like sql.NullString, but I personally would stick to *string. As for awkwardness, it's true that you can't just sp := &"foo" unfortunately. But there is a workaround for this:

func strPtr(s string) *string {
    return &s
}

对 strPtr("foo") 的调用应该是内联的，所以它实际上是 &"foo".

Calls to strPtr("foo") should be inlined, so it's effectively &"foo".

另一种可能是使用new:

sp := new(string)
*sp = "foo"

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