Programming

记录一些在写 Rust 时遇到的错误和重构 Ownership let mut reader = BufReader::new(stream_reader); let mut buffer = String::new(); serde_json::to_writer(&mut stream, &cli.command).unwrap(); stream.flush().unwrap(); reader.read_line(&mut buffer).unwrap(); let response = buffer .trim_end() .to_string() .split(':') .collect::<Vec<&str>>(); 这段代码会在 .to_string() 这里报错, 因为 .trim_end() 返回一个 &str .to_string() 将这个 &str 转换为一个新的临时 String（拥有所有权的新字符串） 在这个临时 String 上调用 .split(’:’)，这会返回一个迭代器，产生 &str 切片 临时 String 在语句结束时被丢弃，导致这些切片变成悬垂引用 修改思路有几种: 直接收集 String let response = buffer .trim_end() .split(':') .map(|s| s.to_string()) .collect::<Vec<String>>(); 直接引用原始的 buffer let response = buffer.trim_end().split(':').collect::<Vec<&str>>(); Generics fn create_engine(engine_name: &str) -> Result<Box<dyn KvsEngine>> { match engine_name { "kvs" => { let kvs = KvStore::open(current_dir()?)?; Ok(Box::new(kvs)) } "sled" => { let sled = SledKvsEngine::new(sled::open("kvs.db")?); Ok(Box::new(sled)) } _ => { panic!("Invalid engine name"); } } } 如果想用泛型的静态分配, 就必须分离引擎的创建逻辑 ...

4 Traits To invoke a trait method, two things must be true: The type must implement the trait. The trait must be in scope. To satisfy the latter, you may have to add a use statement for the trait: use crate::MaybeZero; This is not necessary if: The trait is defined in the same module where the invocation occurs. The trait is defined in the standard library’s prelude. The prelude is a set of traits and types that are automatically imported into every Rust program. It’s as if use std::prelude::*; was added at the beginning of every Rust module. Orphan Rule When a type is defined in another crate (e.g. u32, from Rust’s standard library), you can’t directly define new methods for it. ...

05 Vectors fn array_and_vec() -> ([i32; 4], Vec<i32>) { let a = [10, 20, 30, 40]; // Array // TODO: Create a vector called `v` which contains the exact same elements as in the array `a`. // Use the vector macro. // let v = ??? (a, v) } 这里有几种写法，首先想到的肯定是用一个类似于 for 循环的结构类循环赋值 这里总结一下 Rust 中常见的迭代器 for item in list 会调用 into_iter()，消耗 list 的所有权 for item in &list 会调用 iter()，遍历 list 的引用 for item in &mut list 会调用 iter_mut()，遍历 list 的可变引用 如果想要获取 index, 可以使用 enumerate() 方法: ...