在 Swift 中使用 PropertyListDecoder 时从 plist 解析浮点值时出现解码错误

Question

我想在 plist 中存储一些十进制数，并根据要求检索它们。

plist：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>sessionLength</key>
    <integer>1800</integer>
    <key>name</key>
    <string>Sleeping</string>
    <key>generators</key>
    <array>
        <dict>
            <key>dynamic</key>
            <dict>
                <key>amplitude</key>
                <string>40,35,32,30,28,26,22,14,4</string>
                <key>beat</key>
                <string>3.8,3.3,3.0,3.0,2.8,2.6,2.4,2.0,2.0</string>
                <key>carrier</key>
                <string>1:3,1:5,1:6,1:5,1:6,1:5,1:6,1:4,1:3</string>
                <key>type</key>
                <integer>0</integer>
                <key>isoType</key>
                <integer>0</integer>
                <key>depth</key>
                <string>40,40,40,40,40,40,40,40,40</string>
            </dict>
            <key>static</key>
            <dict>
                <key>amplitude</key>
                <real>45</real>
                <key>beat</key>
                <real>2.4</real>
                <key>carrier</key>
                <real>180.6</real>
                <key>depth</key>
                <integer>40</integer>
                <key>type</key>
                <integer>0</integer>
                <key>isoType</key>
                <integer>0</integer>
            </dict>
        </dict>
        <dict>
            <key>dynamic</key>
            <dict>
                <key>amplitude</key>
                <string>40,40,40,40,40,40,40,40,40</string>
                <key>beat</key>
                <string>3.8,3.8,3.8,3.8,3.8,3.8,3.8,3.8,3.8</string>
                <key>carrier</key>
                <string>2:3,1:5,1:6,1:5,1:6,1:5,1:6,1:4,1:3</string>
                <key>type</key>
                <integer>0</integer>
                <key>isoType</key>
                <integer>0</integer>
                <key>depth</key>
                <string>40,40,40,40,40,40,40,40,40</string>
            </dict>
            <key>static</key>
            <dict>
                <key>amplitude</key>
                <integer>50</integer>
                <key>beat</key>
                <real>2</real>
                <key>carrier</key>
                <real>110</real>
                <key>depth</key>
                <integer>80</integer>
                <key>type</key>
                <integer>0</integer>
                <key>isoType</key>
                <integer>0</integer>
            </dict>
        </dict>
        <dict>
            <key>dynamic</key>
            <dict>
                <key>amplitude</key>
                <string>40,40,40,40,40,40,40,40,40</string>
                <key>beat</key>
                <string>3.8,3.8,3.8,3.8,3.8,3.8,3.8,3.8,3.8</string>
                <key>carrier</key>
                <string>1:5,1:5,1:6,1:5,1:6,1:5,1:6,1:4,1:3</string>
                <key>type</key>
                <integer>1</integer>
                <key>isoType</key>
                <integer>2</integer>
                <key>depth</key>
                <string>70,65,65,50,45,40,40,35,30</string>
            </dict>
            <key>static</key>
            <dict>
                <key>amplitude</key>
                <integer>55</integer>
                <key>beat</key>
                <real>4</real>
                <key>carrier</key>
                <integer>180</integer>
                <key>depth</key>
                <integer>90</integer>
                <key>type</key>
                <integer>0</integer>
                <key>isoType</key>
                <integer>0</integer>
            </dict>
        </dict>
    </array>
</dict>
</plist>

原始数据如下：

我正在使用 Decodable 协议来检索数据。

struct PresetData: Decodable {
    private enum CodingKeys: String, CodingKey {
        case name, sessionLength, generators
    }
    
    let name: String
    let sessionLength: Int
    let generators: [PresetStoredData]
}

struct PresetStoredData: Decodable {
    private enum CodingKeys: String, CodingKey {
        case `static`, dynamic
    }
    
    let `static`: PresetStoredItem
    let dynamic: PresetStoredDynamicItem
}

struct PresetStoredItem: Decodable {
    private enum CodingKeys: String, CodingKey {
        case amplitude, beat, carrier, depth, type, isoType
    }
    
    let amplitude: Float
    let beat: Float
    let carrier: Float
    let depth: Float
    
    let type: Int
    let isoType: Int
}

struct PresetStoredDynamicItem: Decodable {
    private enum CodingKeys: String, CodingKey {
        case amplitude, beat, carrier, depth, type, isoType
    }
    
    let amplitude: String
    let beat: String
    let carrier: String
    let depth: String
    
    let type: Int
    let isoType: Int
}

结果是“已解析的属性列表编号 <2.4> 不适合 Float。”

编辑：解析方法：

let decoder = PropertyListDecoder()
    return try! decoder.decode(PresetData.self, from: data)

这对我来说有点不合理。知道哪里出了问题吗？

Answer 1

将浮点类型声明为 Double 而不是 Float

struct PresetStoredItem: Decodable {
    
    let amplitude: Double
    let beat: Double
    let carrier: Double
    let depth: Double
    
    let type: Int
    let isoType: Int
}

如果所有键都与结构名称匹配，则可以省略 CodingKeys

Answer 2

考虑

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>amplitude</key>
    <real>45.0</real>
    <key>beat</key>
    <real>4.2</real>
    <key>carrier</key>
    <real>180.6</real>
</dict>
</plist>

如果你解码：

struct Preset: Decodable {
    let amplitude: Float
    let beat: Float
    let carrier: Float
}

您将收到

dataCorrupted(Swift.DecodingError.Context(codingPath: [CodingKeys(stringValue: "beat", intValue: nil)], debugDescription: "Parsed property list number <4.2> does not fit in Float.", underlyingError: nil))

但是如果你把它改成Double，它会起作用：

struct Preset: Decodable {
    let amplitude: Double
    let beat: Double
    let carrier: Double
}

在 Swift 中使用 PropertyListDecoder 时从 plist 解析浮点值时出现解码错误

Decoding Error when parsing float value from plist when using PropertyListDecoder in Swift

ios

swift

plist