Rust，使用枚举从 HashMap 获取值

以下是一些反馈:

• 如果您已经处理了所有选项，则不要包括_个默认匹配大小写.它将隐藏future 的错误.
• 如果每个成员都只是一种数据类型，则不要将变量命名为DataTypes.把它命名为DataType.
• result必须是一个特定的类型.枚举的全部意义在于您可以分别处理不同的值，因此将它们组合在result类型中是没有意义的.当然，can保留result个DataType对象，并为其实现Debug/Display，这就是我将在重新编写的代码中如何做到这一点.
• 虽然您先can查询键，然后在循环中再次查询值，但这相当慢.您可以立即迭代键-值对.这样，您就避免了许多unwrap()，这使得您的代码更不容易出错.

use std::collections::HashMap;

#[derive(Debug)]
enum DataType {
    String(String),
    Bool(bool),
}

fn get_hashmap() -> Result<HashMap<String, DataType>, ()> {
    let data = HashMap::from([
        (
            "password".to_string(),
            DataType::String("password".to_string()),
        ),
        (
            "username".to_string(),
            DataType::String("Fun username".to_string()),
        ),
        ("is_blocked".to_string(), DataType::Bool(true)),
        ("is_confirmed".to_string(), DataType::Bool(false)),
    ]);
    Ok(data)
}
fn main() {
    let data = get_hashmap().unwrap();
    for (key, value) in data {
        println!("{}: {:?}", key, value);

        match value {
            DataType::Bool(value) => {
                println!("\tValue was a bool: {}", value);
                // do something if the value is a bool
            }
            DataType::String(value) => {
                println!("\tValue was a string: {}", value);
                // do something if the value is a string,
            } /*
               * Don't include a default case. That way the compiler
               * will remind you to handle additional enum entries if
               * you add them in the future.
               * Adding a default case is only a good practice in languages
               * where matching is not exhaustive.
               */
        };
    }
}

username: String("Fun username")
        Value was a string: Fun username
is_confirmed: Bool(false)
        Value was a bool: false
is_blocked: Bool(true)
        Value was a bool: true
password: String("password")
        Value was a string: password

不过，不要担心，您不需要在使用此枚举的任何地方都使用match，否则与两个单独的哈希图相比，您不会获得太多好处.相反，您可以为所有枚举条目定义共享功能，并隐藏其中的match.就像这样:

use std::collections::HashMap;

#[derive(Debug)]
enum DataType {
    String(String),
    Bool(bool),
}

impl DataType {
    fn do_something(&self) {
        match self {
            DataType::Bool(value) => {
                println!("\tDo something with boolean '{}'!", value);
            }
            DataType::String(value) => {
                println!("\tDo something with string {:?}!", value);
            }
        };
    }
}

fn get_hashmap() -> Result<HashMap<String, DataType>, ()> {
    let data = HashMap::from([
        (
            "password".to_string(),
            DataType::String("password".to_string()),
        ),
        (
            "username".to_string(),
            DataType::String("Fun username".to_string()),
        ),
        ("is_blocked".to_string(), DataType::Bool(true)),
        ("is_confirmed".to_string(), DataType::Bool(false)),
    ]);
    Ok(data)
}

fn main() {
    let data = get_hashmap().unwrap();
    for (key, value) in data {
        println!("{}: {:?}", key, value);
        value.do_something();
    }
}

is_confirmed: Bool(false)
        Do something with boolean 'false'!
password: String("password")
        Do something with string "password"!
is_blocked: Bool(true)
        Do something with boolean 'true'!
username: String("Fun username")
        Do something with string "Fun username"!

如果您的目标是将序列化/反序列化添加到您的 struct 中(就像您在这里手动实现的那样)，让我提示您接近serde，它已经免费处理了大部分序列化.

如本例所示(它可能是也可能不是您的 struct 的样子)，它将您的 struct 序列化到JSON和从JSON序列化:

use serde::{Deserialize, Serialize};

#[derive(Serialize, Deserialize)]
struct User {
    username: String,
    password: String,
    is_blocked: bool,
    is_confirmed: bool,
}

fn main() {
    let user = User {
        username: "Fun username".to_string(),
        password: "password".to_string(),
        is_blocked: true,
        is_confirmed: false,
    };

    let user_serialized = serde_json::to_string(&user).unwrap();
    println!("Serialized: {}", user_serialized);

    let user_deserialized: User = serde_json::from_str(&user_serialized).unwrap();
    println!("Name: {}", user_deserialized.username);
}

Serialized: {"username":"Fun username","password":"password","is_blocked":true,"is_confirmed":false}
Name: Fun username