Rust 编程中的 HashMap
HashMap是一种重要的数据结构,因为它允许我们以键值对的形式存储数据。在Rust中,HashMap按键存储值。
HashMap键可以是布尔值、整数、字符串或任何其他实现Eq和Hash特征的数据类型。
HashMap的大小可以增长,当空间变得过多时,它们也可以自行缩小。
我们可以通过多种方式创建HashMap,我们可以使用HashMap::with_capacity(uint)或HashMap::new()。
以下是HashMaps支持的方法:
insert()
get()
remove()
iter()
示例
让我们看一个例子,我们构建一个HashMap并使用上述所有这些操作。
考虑下面显示的示例。
use std::collections::HashMap; fn call(number: &str) -> &str { match number { "798-133" => "We're sorry. Please hang up and try again.", "645-7698" => "Hello, What can I get for you today?", _ => "Hi! Who is this again?" } } fn main() { let mut contacts = HashMap::new(); contacts.insert("Mukul", "798-133"); contacts.insert("Mayank", "645-7698"); contacts.insert("Karina", "435-8291"); contacts.insert("Rahul", "956-1745"); match contacts.get(&"Mukul") { Some(&number) => println!("Calling Mukul: {}", call(number)), _ => println!("Don't have Mukul's number."), } //`HashMap::insert()`返回`None` contacts.insert("Mukul", "164-6743"); match contacts.get(&"Mayank") { Some(&number) => println!("Calling Mayank: {}", call(number)), _ => println!("Don't have Mayank's number."), } contacts.remove(&"Mayank"); //`HashMap::iter()`返回一个迭代器,它产生 // (&'a key, &'a value) pairs in arbitrary order. for (contact, &number) in contacts.iter() { println!("Calling {}: {}", contact, call(number)); } }输出结果
Calling Mukul: We're sorry. Please hang up and try again. Calling Mayank: Hello, What can I get for you today? Calling Mukul: Hi! Who is this again? Calling Karina: Hi! Who is this again? Calling Rahul: Hi! Who is this again?