【Rust】HashMap
1. new
2. 所有权
3. get
4. iterator
5. insert
6. or_insert
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1. new
let mut scores = HashMap::new(); scores.insert(String::from("Blue"), 10);
2. 所有权
let key: String = String::from("key1"); let value: String = String::from("value2"); let mut scores = HashMap::new(); // 对于像 String 这样拥有所有权的值,其值将被移动而哈希 map 会成为这些值的所有者 scores.insert(key, value); // println!("{},{}",key,value); // key和value不再有效
3. get
let mut scores = HashMap::new(); scores.insert(String::from("name"), String::from("Tom Smith")); let k = String::from("name"); let v: Option<&String> = scores.get(&k); match v { Some(x) => println!("{}",x), None => println!("none value"), }
4. iterator
let mut scores = HashMap::new(); scores.insert(String::from("name"), String::from("Tom Smith")); for (key, value) in &scores { println!("{}: {}", key, value); }
5. insert
let mut scores = HashMap::new(); scores.insert(String::from("name"), String::from("Tom Smith")); scores.insert(String::from("name"), String::from("Tom Smith 2"));// 使用新值覆盖老值 println!("{:?}", scores);
6. or_insert
let mut scores = HashMap::new(); scores.insert(String::from("name"), String::from("Tom Smith")); scores.entry(String::from("name")).or_insert(String::from("Tom Smith 2"));// 不存在时才插入,存在返回这个值的可变引用 println!("{:?}", scores);
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