[英]Rust disable struct construction
How can I disable struct construction but maintaining pattern matching in Rust?如何在 Rust 中禁用结构构造但保持模式匹配?
Let's see an example:让我们看一个例子:
struct OrderedPair(pub u32, pub u32);
impl OrderedPair {
fn new(a: u32, b: u32) -> Self {
if a < b {
Self(a, b)
} else {
Self(b, a)
}
}
}
It's obvious that I want to inhibit the construction of such struct (eg OrderedPair(2, 1)
) and to use only the new
method, in order to preserve the invariant.很明显,我想禁止构建这种结构(例如OrderedPair(2, 1)
)并只使用new
方法,以保持不变性。 I know of 3 ways to do this:我知道 3 种方法可以做到这一点:
struct OrderedPair(u32, u32);
struct OrderedPair(pub u32, pub u32, ());
#[non_exhaustive]
struct OrderedPair(pub u32, pub u32);
The issues are that with 1 I cannot access the members at all and with all three I cannot use pattern matching问题是 1 我根本无法访问成员,而所有三个我都无法使用模式匹配
let OrderedPair(min, max) = my_ordered_pair;
So is there a way to block struct construction but allow pattern matching?那么有没有办法阻止结构构造但允许模式匹配?
I know that if we declare a mutable variable of that type with public access to members then the invariant can be broken by manually changing the members, but for now avoiding the struct constructor is enough.我知道,如果我们声明一个具有对成员的公共访问权限的该类型的可变变量,那么可以通过手动更改成员来破坏不变量,但现在避免使用 struct 构造函数就足够了。
Instead of doing pattern matching directly on the fields, you can do it on a returned tupple:您可以在返回的元组上进行,而不是直接在字段上进行模式匹配:
#[derive(Clone, Copy)]
pub struct OrderedPair {
a: u32,
b: u32,
}
impl OrderedPair {
pub fn content(self) -> (u32, u32) {
(self.a, self.b)
}
}
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