語境

在通過使用其 XML 描述讀取二進制檔案時嘗試找到一種更簡單的方式來處理轉換為 rust 型別時，建議使用帶有單元型別的列舉而不是反序列化字串或 &str，以獲得更多的編譯器保證和避免一生；但是，讓 XML 直接反序列化到列舉單元變體中會導致一些問題。

XML 檔案

<Records>
    <Record>
        <name>Single</name>
        <number>1</number>
        <location>0</location>
        <data_type>IEEE754LSBSingle</data_type>
        <length>4</length>
    </Record>
    <Record>
        <name>Double</name>
        <number>2</number>
        <location>4</location>
        <data_type>IEEE754LSBDouble</data_type>
        <length>8</length>
    </Record>
    <Record>
        <name>SingleArr</name>
        <number>3</number>
        <location>11</location>
        <data_type>IEEE754LSBSingleArr</data_type>
        <length>8</length>
    </Record>
    <Record>
        <name>DoubleArr</name>
        <number>4</number>
        <location>18</location>
        <data_type>IEEE754LSBDoubleArr</data_type>
        <length>16</length>
    </Record>
</Records>

編碼

use binary_type_cast::PrettyPrint;
use quick_xml::{de::from_reader, DeError};
use serde::{Deserialize};
use std::{fs::File, io::BufReader};

#[derive(Clone, Copy, Debug, Deserialize)]
//#[serde(tag="data_type")]
//#[serde(untagged)]
pub enum DataTypes {
    // 4 bytes
    IEEE754LSBSingle,
    // 8 bytes
    IEEE754LSBDouble,
    // [4 bytes, 4 bytes]
    IEEE754LSBSingleArr,
    // [8 bytes, 8 bytes]
    IEEE754LSBDoubleArr,
    // Include ASCIIString just to make sure records are still gathered even if none of them use this
    ASCIIString,
}

#[derive(Debug, Deserialize)]
pub struct Records {
    #[serde(rename="Record")]
    pub records: Vec<Record>,
}

#[derive(Debug, Deserialize)]
pub struct Record {
    pub name: String,
    pub number: u32,
    pub location: u32,
    //#[serde(flatten)]
    pub data_type: DataTypes,
    pub length: u32
}

pub fn get_xml_record(file: &File) -> Result<Records, DeError> {
    let reader = BufReader::new(file);    
    let records: Records = from_reader(reader).unwrap();
    Ok(records)
}

fn main() {
    let description = "./data/desc.xml";
    if let Ok(file) = File::open(description) {
        if let Ok(records) = get_xml_record(&file) {
            println!("{:#?}",records);

        }
    }

}

我試圖實作在呈現的代碼中看到的注釋掉的 serde 屬性的各種組合。似乎創建一個自定義反序列化器將匹配 XML 中的字串，然后輸出相關的 DataTypes 變體，這基本上會復制原始帖子在另一個問題中的行為，其中字串被手動匹配和轉換。

uj5u.com熱心網友回復：

這似乎是一個錯誤quick-xml

我不用大驚小怪地使用它來作業serde-xml-rs：

use serde_xml_rs::from_str;
use serde::Deserialize;

#[derive(Clone, Copy, Debug, Deserialize)]
pub enum DataTypes {
    // 4 bytes
    IEEE754LSBSingle,
    // 8 bytes
    IEEE754LSBDouble,
    // [4 bytes, 4 bytes]
    IEEE754LSBSingleArr,
    // [8 bytes, 8 bytes]
    IEEE754LSBDoubleArr,
    // Include ASCIIString just to make sure records are still gathered even if none of them use this
    ASCIIString,
}

#[derive(Debug, Deserialize)]
pub struct Records {
    #[serde(rename = "$value")]
    pub records: Vec<Record>,
}

#[derive(Debug, Deserialize)]
pub struct Record {
    pub name: String,
    pub number: u32,
    pub location: u32,
    pub data_type: DataTypes,
    pub length: u32
}

fn main() {
    let source = r##"
<Records>
    <Record>
        <name>Single</name>
        <number>1</number>
        <location>0</location>
        <data_type>IEEE754LSBSingle</data_type>
        <length>4</length>
    </Record>
    <Record>
        <name>Double</name>
        <number>2</number>
        <location>4</location>
        <data_type>IEEE754LSBDouble</data_type>
        <length>8</length>
    </Record>
    <Record>
        <name>SingleArr</name>
        <number>3</number>
        <location>11</location>
        <data_type>IEEE754LSBSingleArr</data_type>
        <length>8</length>
    </Record>
    <Record>
        <name>DoubleArr</name>
        <number>4</number>
        <location>18</location>
        <data_type>IEEE754LSBDoubleArr</data_type>
        <length>16</length>
    </Record>
</Records>
    "##;

    let records: Records = from_str(source).unwrap();
    dbg!(records);
}

輸出：

[src\main.rs:71] records = Records {
    records: [
        Record {
            name: "Single",
            number: 1,
            location: 0,
            data_type: IEEE754LSBSingle,
            length: 4,
        },
        Record {
            name: "Double",
            number: 2,
            location: 4,
            data_type: IEEE754LSBDouble,
            length: 8,
        },
        Record {
            name: "SingleArr",
            number: 3,
            location: 11,
            data_type: IEEE754LSBSingleArr,
            length: 8,
        },
        Record {
            name: "DoubleArr",
            number: 4,
            location: 18,
            data_type: IEEE754LSBDoubleArr,
            length: 16,
        },
    ],
}

標籤：xml序列化锈枚举塞尔德

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