peek 为您提供了一个引用，该引用指向可由 next() 调用消费的即将可用的项目，而 peek_n 允许您预览 n 次。调用 peek_n(0) 与调用 peek 相同。

peek 和 peek_n 是幂等的，这意味着在 BPeekable 上重复调用它们对底层迭代器或 BPeekable 的任何状态都没有影响。如果您发现违反此合同的问题，请提交问题。

用法

将 better_peekable 添加到您的 Cargo.toml。

[dependencies]
better_peekable = "0.2.4"

我们将使用以下序列的 peek 和 peek_n 调用来测试 BPeekable 的幂等性。

// Required for peek and peek_n 
use better_peekable::BetterPeekable;

fn main() {
    let vec = vec![
            String::from("Hello"),
            String::from("World"),
            String::from("It's a nice day to make"),
            String::from("A better peekable iterator adaptor"),
            String::from("Peek_N and Peek are supposed to be"),
            String::from("Idempotent Methods"),
        ];

        let mut iter = vec.into_iter();
        let mut better_peeker = iter.better_peekable();
       
        assert_eq!(better_peeker.peek(), Some(&"Hello".to_string()));
        assert_eq!(better_peeker.peek(), Some(&"Hello".to_string()));
        assert_eq!(better_peeker.peek(), Some(&"Hello".to_string()));
        assert_eq!(better_peeker.peek_n(1), Some(&"World".to_string()));
        assert_eq!(better_peeker.next(), Some("Hello".to_string()));
        assert_eq!(better_peeker.next(), Some("World".to_string()));
        assert_eq!(
            better_peeker.peek(),
            Some(&"It's a nice day to make".to_string())
        );
        assert_eq!(
            better_peeker.peek_n(0),
            Some(&"It's a nice day to make".to_string())
        );
        assert_eq!(
            better_peeker.peek_n(1),
            Some(&"A better peekable iterator adaptor".to_string())
        );
        assert_eq!(
            better_peeker.nth(1),
            Some("A better peekable iterator adaptor".to_string())
        );
        assert_eq!(
            better_peeker.peek_n(1),
            Some(&"Idempotent Methods".to_string())
        );

变更日志 0.2.4

从 Iterator::Item 中移除了 trait 约束 std::fmt::Debug