如何存储预计算的SKPhysicsBody数组，避免重复计算提升旧设备性能？

我在应用首次加载时于后台线程运行代码，提前生成SKPhysicsBody数组供节点加载时使用（参考Stack Overflow中@mfessenden关于SKPhysicsBody纹理动画的实现），以此提升性能。新设备上该操作可在应用intro阶段完成，影响不大，但旧设备可能因计算超时影响性能。我尝试将计算后的数组存储至UserDefaults，却触发NSInvalidArgumentException错误（提示插入非属性列表对象）。请问何种方式可存储该数据，使其仅需计算一次？

代码示例：

var Sat1shapes: [SKPhysicsBody] = []
var Sat1Frames: [SKTexture] = []

for frame in Sat1Frames {
    let node6 = SKSpriteNode()
    node6.physicsBody = SKPhysicsBody(texture: frame, size: CGSize(width: 414 * wR, height: 233 * hR))
    Sat1shapes.append(node6.physicsBody!)
}

let Sat2AnimatedAtlas = SKTextureAtlas(named: "satsmall2")
let numImagesSat2 = Sat2AnimatedAtlas.textureNames.count
for i in 0...numImagesSat2 {
    let Sat2TextureName = "\(i)"
    Sat2Frames.append(Sat2AnimatedAtlas.textureNamed(Sat2TextureName))
}

解决方案 #

方法1：使用归档（NSKeyedArchiver/NSKeyedUnarchiver） #

SKPhysicsBody遵循NSCoding协议，可将数组归档为Data后存储，支持存入UserDefaults或本地文件。

归档存储代码：

// 归档Sat1shapes数组
do {
    let data = try NSKeyedArchiver.archivedData(withRootObject: Sat1shapes, requiringSecureCoding: false)
    UserDefaults.standard.set(data, forKey: "StoredSat1PhysicsBodies")
} catch {
    print("归档失败：\(error)")
}

解归档读取代码：

// 启动时读取已存储的数组
if let data = UserDefaults.standard.data(forKey: "StoredSat1PhysicsBodies") {
    do {
        if let storedShapes = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? [SKPhysicsBody] {
            Sat1shapes = storedShapes
            // 无需再重新计算
        }
    } catch {
        print("解归档失败：\(error)")
        generatePhysicsBodies()
    }
} else {
    // 无存储数据时重新计算
    generatePhysicsBodies()
}

// 封装生成物理体的函数
func generatePhysicsBodies() {
    for frame in Sat1Frames {
        let node6 = SKSpriteNode()
        node6.physicsBody = SKPhysicsBody(texture: frame, size: CGSize(width: 414 * wR, height: 233 * hR))
        Sat1shapes.append(node6.physicsBody!)
    }
}

方法2：存储物理体生成参数（更轻量可靠） #

若归档出现兼容性问题，可存储生成SKPhysicsBody的关键参数，下次直接重建：

1. 记录每个物理体对应的纹理名称、尺寸等参数
2. 启动时读取参数，重新从图集加载纹理并生成物理体

示例代码：

// 存储参数：假设Sat1Frames来自名为"sat1Atlas"的纹理图集
let sat1TextureNames = Sat1Frames.map { $0.name ?? "" }
UserDefaults.standard.set(sat1TextureNames, forKey: "Sat1TextureNames")
UserDefaults.standard.set(["width": 414 * wR, "height": 233 * hR], forKey: "Sat1PhysicsSize")

// 读取并重建
if let textureNames = UserDefaults.standard.array(forKey: "Sat1TextureNames") as? [String],
   let sizeDict = UserDefaults.standard.dictionary(forKey: "Sat1PhysicsSize") as? [String: CGFloat],
   let width = sizeDict["width"], let height = sizeDict["height"] {
    let size = CGSize(width: width, height: height)
    let atlas = SKTextureAtlas(named: "sat1Atlas")
    Sat1shapes = textureNames.compactMap { name in
        let texture = atlas.textureNamed(name)
        return SKPhysicsBody(texture: texture, size: size)
    }
} else {
    generatePhysicsBodies()
}

方法3：本地文件存储（适合大数据量） #

若SKPhysicsBody数组较大，可直接将归档数据存入应用Documents目录：

存储代码：

do {
    let data = try NSKeyedArchiver.archivedData(withRootObject: Sat1shapes, requiringSecureCoding: false)
    let documentsDir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
    let fileURL = documentsDir.appendingPathComponent("Sat1PhysicsBodies.data")
    try data.write(to: fileURL)
} catch {
    print("写入文件失败：\(error)")
}

读取代码：

let documentsDir = FileManager.default.urls(for: .documentDirectory, in: .userDomainMask).first!
let fileURL = documentsDir.appendingPathComponent("Sat1PhysicsBodies.data")
if FileManager.default.fileExists(atPath: fileURL.path) {
    do {
        let data = try Data(contentsOf: fileURL)
        if let storedShapes = try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(data) as? [SKPhysicsBody] {
            Sat1shapes = storedShapes
        }
    } catch {
        print("读取文件失败：\(error)")
        generatePhysicsBodies()
    }
} else {
    generatePhysicsBodies()
}

内容的提问来源于stack exchange，提问作者Guitarman4