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包含了一些Iterator的常用处理方法
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## 遍历同时获取元素的索引
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```rust
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let mut xs = vec![1i32, 2, 3];
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for (i, x) in xs.iter().enumerate() {
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println!("In position {} we have value {}", i, x);
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}
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```
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## 几种从Vec生成Iterator的方式
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1. iter返回的是值的不可变引用，即&T
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2. iter_mut返回的是可变引用，即&mut T
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3. into_iter返回的是T类型的值
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```rust
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let mut v = [String::from("a"), String::from("a"), String::from("a")];
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// - move occurs because `v` has type `Vec<String>`, which does not implement the `Copy
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//`v` moved due to this method call
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for x in v.into_iter() {
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println!("{:?}", x)
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}
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// Error: borrow of moved value: `v`
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println!("{:?}", v)
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```
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## 忽略Vec中失败的Result
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`filter_map` calls a function and filters out the results that are `None`
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```rust
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fn main() {
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let strings = vec!["tofu", "93", "18"];
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let numbers: Vec<_> = strings
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.into_iter()
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.filter_map(|s| s.parse::<i32>().ok())
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.collect();
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println!("Results: {:?}", numbers);
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}
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```
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## 遍历Vec时，失败直接返回
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`Result` implements `FromIter` so that a vector of results (`Vec<Result<T, E>>`) can be turned into a result with a vector (`Result<Vec<T>, E>`). Once an `Result::Err` is found, the iteration will terminate
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```rust
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fn main() {
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let strings = vec!["tofu", "93", "18"];
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let numbers: Result<Vec<_>, _> = strings
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.into_iter()
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.map(|s| s.parse::<i32>())
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.collect();
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println!("Results: {:?}", numbers);
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}
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```
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This same technique can be used with `Option`.
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## 遍历Vec时，收集所有的正确值和错误值
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```rust
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fn main() {
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let strings = vec!["tofu", "93", "18"];
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let (numbers, errors): (Vec<_>, Vec<_>) = strings
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.into_iter()
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.map(|s| s.parse::<i32>())
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.partition(Result::is_ok);
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let numbers: Vec<_> = numbers.into_iter().map(Result::unwrap).collect();
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let errors: Vec<_> = errors.into_iter().map(Result::unwrap_err).collect();
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println!("Numbers: {:?}", numbers);
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println!("Errors: {:?}", errors);
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}
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``` |
