如何扩展float3或任何其他内置类型以符合Codable协议？ [英] How to extend float3 or any other built-in type to conform to the Codable protocol?
问题描述
在尝试使用基本JSONEncoder序列化float3对象数组时，发现float3不符合Codable协议，因此无法完成。
In trying to serialize an array of float3 objects with the basic JSONEncoder, it's revealed that float3 does not conform to the Codable protocol, so this cannot be done.
我试图按照对自定义类型进行编码和解码中的建议编写基本扩展如下所示，但是在初始化所有存储的属性之前使用的错误'self'会为init中的每个赋值行呈现。我认为这是因为编译器不确定在初始化float3之前是否定义了 Float.self ，但是我不确定如何解决此问题。
I tried to write a basic extension as suggested in Encoding and Decoding Custom Types as seen below, but the error 'self' used before all stored properties are initialized is rendered for each of the assignment lines in the init. I assume this is because the compiler is not sure that Float.self is defined prior to the initialization of float3, but I'm not sure how to resolve this.
此外，init的结尾表示从初始化器返回而未初始化所有存储的属性，我认为这意味着除了x，y和z之外的float3属性，但我想知道是否存在一种方法来默认/忽略这些属性，和/或除了在simd中挖掘所有float3扩展之外，如何找到属性的完整列表。
Further, the end of the init says Return from initializer without initializing all stored properties which I assume means there are float3 properties in addition to x, y, and z, but I'm wondering if there is a way to default/ignore these, and/or how to find the full list of properties aside from digging through all the float3 extensions in simd.
如果您对如何执行此操作有任何想法，欢迎与他们分享。谢谢！
If you have any thoughts about how to go about doing this, sharing them would be much appreciated. Thanks!
import SceneKit
extension float3: Codable {
public init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
x = try values.decode(Float.self, forKey: .x)
y = try values.decode(Float.self, forKey: .y)
z = try values.decode(Float.self, forKey: .z)
}
public func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(x, forKey: .x)
try container.encode(y, forKey: .y)
try container.encode(z, forKey: .z)
}
enum CodingKeys: String, CodingKey {
case x
case y
case z
}
}
这是（ simd文件中的float3定义：
Here is the (I think complete) float3 definitions from the simd file:
/// A vector of three `Float`. This corresponds to the C and
/// Obj-C type `vector_float3` and the C++ type `simd::float3`.
public struct float3 {
public var x: Float
public var y: Float
public var z: Float
/// Initialize to the zero vector.
public init()
/// Initialize a vector with the specified elements.
public init(_ x: Float, _ y: Float, _ z: Float)
/// Initialize a vector with the specified elements.
public init(x: Float, y: Float, z: Float)
/// Initialize to a vector with all elements equal to `scalar`.
public init(_ scalar: Float)
/// Initialize to a vector with elements taken from `array`.
///
/// - Precondition: `array` must have exactly three elements.
public init(_ array: [Float])
/// Access individual elements of the vector via subscript.
public subscript(index: Int) -> Float
}
extension float3 : Equatable {
/// True iff every element of lhs is equal to the corresponding element of
/// rhs.
public static func ==(lhs: float3, rhs: float3) -> Bool
}
extension float3 : CustomDebugStringConvertible {
/// Debug string representation
public var debugDescription: String { get }
}
extension float3 : ExpressibleByArrayLiteral {
/// Initialize using `arrayLiteral`.
///
/// - Precondition: the array literal must exactly three
/// elements.
public init(arrayLiteral elements: Float...)
}
extension float3 : Collection {
/// The position of the first element in a nonempty collection.
///
/// If the collection is empty, `startIndex` is equal to `endIndex`.
public var startIndex: Int { get }
/// The collection's "past the end" position---that is, the position one
/// greater than the last valid subscript argument.
///
/// When you need a range that includes the last element of a collection, use
/// the half-open range operator (`..<`) with `endIndex`. The `..<` operator
/// creates a range that doesn't include the upper bound, so it's always
/// safe to use with `endIndex`. For example:
///
/// let numbers = [10, 20, 30, 40, 50]
/// if let index = numbers.index(of: 30) {
/// print(numbers[index ..< numbers.endIndex])
/// }
/// // Prints "[30, 40, 50]"
///
/// If the collection is empty, `endIndex` is equal to `startIndex`.
public var endIndex: Int { get }
/// Returns the position immediately after the given index.
///
/// The successor of an index must be well defined. For an index `i` into a
/// collection `c`, calling `c.index(after: i)` returns the same index every
/// time.
///
/// - Parameter i: A valid index of the collection. `i` must be less than
/// `endIndex`.
/// - Returns: The index value immediately after `i`.
public func index(after i: Int) -> Int
}
extension float3 {
/// Vector (elementwise) sum of `lhs` and `rhs`.
public static func +(lhs: float3, rhs: float3) -> float3
/// Vector (elementwise) difference of `lhs` and `rhs`.
public static func -(lhs: float3, rhs: float3) -> float3
/// Negation of `rhs`.
prefix public static func -(rhs: float3) -> float3
/// Elementwise product of `lhs` and `rhs` (A.k.a. the Hadamard or Schur
/// vector product).
public static func *(lhs: float3, rhs: float3) -> float3
/// Scalar-Vector product.
public static func *(lhs: Float, rhs: float3) -> float3
/// Scalar-Vector product.
public static func *(lhs: float3, rhs: Float) -> float3
/// Elementwise quotient of `lhs` and `rhs`.
public static func /(lhs: float3, rhs: float3) -> float3
/// Divide vector by scalar.
public static func /(lhs: float3, rhs: Float) -> float3
/// Add `rhs` to `lhs`.
public static func +=(lhs: inout float3, rhs: float3)
/// Subtract `rhs` from `lhs`.
public static func -=(lhs: inout float3, rhs: float3)
/// Multiply `lhs` by `rhs` (elementwise).
public static func *=(lhs: inout float3, rhs: float3)
/// Divide `lhs` by `rhs` (elementwise).
public static func /=(lhs: inout float3, rhs: float3)
/// Scales `lhs` by `rhs`.
public static func *=(lhs: inout float3, rhs: Float)
/// Scales `lhs` by `1/rhs`.
public static func /=(lhs: inout float3, rhs: Float)
}
推荐答案
您可以解决编译器错误，而不是尝试直接将解码后的值分配给您类型的字段，将解码后的值存储在局部变量中，然后调用指定的 float3 。
You can solve the compiler error by instead of trying to directly assign the decoded values to the fields of your type, storing the decoded values in local variables, then calling a designated initializer of float3.
Rob在他的答案，问题的原因与 x ， y 和 z 是计算的属性，而不是存储的属性，因此它们不能在初始化期间直接写入。
As Rob mentions in his answer, the cause of the issue has to do with x, y and z being computed properties rather than stored ones, so they cannot be directly written during initialization.
extension float3: Codable {
public init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
let x = try values.decode(Float.self, forKey: .x)
let y = try values.decode(Float.self, forKey: .y)
let z = try values.decode(Float.self, forKey: .z)
self.init(x, y, z)
}
public func encode(to encoder: Encoder) throws {
var container = encoder.container(keyedBy: CodingKeys.self)
try container.encode(x, forKey: .x)
try container.encode(y, forKey: .y)
try container.encode(z, forKey: .z)
}
private enum CodingKeys: String, CodingKey {
case x,y,z
}
}
您可以使用以下代码在Playground中测试编码和解码：
You can test both encoding and decoding in a Playground using below code:
let vector = float3(3, 2.4, 1)
do {
let encodedVector = try JSONEncoder().encode(vector)
let jsonVector = String(data: encodedVector, encoding: .utf8) //"{"x":3,"y":2.4000000953674316,"z":1}"
let decodedVector = try JSONDecoder().decode(float3.self, from: encodedVector) //float3(3.0, 2.4, 1.0)
} catch {
print(error)
}
如果您希望使用更简洁的代码，可以将 init（from解码器：）方法简化为：
If you prefer more concise code, the init(from decoder:) method can be shortened to:
public init(from decoder: Decoder) throws {
let values = try decoder.container(keyedBy: CodingKeys.self)
try self.init(values.decode(Float.self, forKey: .x), values.decode(Float.self, forKey: .y), values.decode(Float.self, forKey: .z))
}
这篇关于如何扩展float3或任何其他内置类型以符合Codable协议？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！
