[英]How does Rust know which trait methods are required or provided?
From the std::iter::Iterator
documentation, I can see that only the next
method is required: 从
std::iter::Iterator
文档中,我可以看到只需要next
方法:
Required Methods
所需方法
fn next(&mut self) -> Option<Self::Item>
But from the source code , after removing comments: 但是从源代码中 ,删除注释后:
pub trait Iterator {
/// The type of the elements being iterated over.
#[stable(feature = "rust1", since = "1.0.0")]
type Item;
......
#[stable(feature = "rust1", since = "1.0.0")]
fn next(&mut self) -> Option<Self::Item>;
......
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
fn size_hint(&self) -> (usize, Option<usize>) { (0, None) }
......
}
I can see, except for the #[inline]
attribute, there is no difference between required and provided methods. 我可以看到,除了
#[inline]
属性,必需方法和提供的方法之间没有区别。 How does Rust know which method is required or provided? Rust如何知道需要或提供哪种方法?
except for the
#[inline]
attribute, there is no difference between required and provided methods除了
#[inline]
属性,必需方法和提供的方法之间没有区别
There is a huge difference, you just are ignoring the (lack of) formatting. 两者之间存在巨大差异,您只是忽略了格式的不足。 Allow me to reformat for you:
请允许我为您重新格式化:
fn next(&mut self) -> Option<Self::Item>;
fn size_hint(&self) -> (usize, Option<usize>) { // Starting with `{`
(0, None) //
} // Ending with `}`
All the default methods have a function body . 所有默认方法都有一个函数体 。 The required methods do not.
所需的方法没有。
I'd highly recommend rereading The Rust Programming Language , specifically the chapter about traits and default implementations . 我强烈建议您重新阅读Rust编程语言 ,特别是有关特征和默认实现的章节 。 This resource is a much better way to get started with introductory topics like this than reading arbitrary snippets of the standard library.
与阅读标准库的任意代码片段相比,此资源是入门这类入门主题的更好方法。
It is rather simple: the provided (optional) functions have a default implementation, not the required. 这非常简单:提供的(可选)功能具有默认实现,而不是必需的。
Note that you can re-implement the provided functions if you wish so it can perform better than the default one for your particular struct/enum. 请注意,您可以根据需要重新实现所提供的功能,以使其比特定结构/枚举的默认功能更好。
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.