JSON encode non primitive types in Swift

Question

Helo I would like to encode non standard types such as sims_float3x3 and [vector_float3] . What is the recommended way to this?

I tried to use Struct like so,

struct Example: Codable {
    var test_var1:simd_float3x3
    var test_var2:[vector_float3]
}

I get the error, does not conform to protocol 'Decodable'

I also tried,

let data = try encoder.encode(test_var1)

I get the error - Argument type 'simd_float3x3' does not conform to expected type 'Encodable'

I currently can do like so,

let data_col1 = try encoder.encode(test_var1.columns.0) // simd_float3
let data_col2 = try encoder.encode(test_var1.columns.1) // simd_float3
let data_col3 = try encoder.encode(test_var1.columns.2) // simd_float3

But is there any way to do this more elegantly / efficiently?

Answer 1

You can use the same technique as shown in this answer for the outer array:

import SceneKit

extension simd_float3x3: Codable {
    public init(from decoder: Decoder) throws {
        var container = try decoder.unkeyedContainer()
        try self.init(container.decode([float3].self))
    }
    public func encode(to encoder: Encoder) throws {
        var container = encoder.unkeyedContainer()
        try container.encode([columns.0, columns.1, columns.2])
     }
 }

---

Playground testing

let simdFloat = simd_float3x3(float3(0, 1, 2), float3(3,4, 5), float3(6, 7, 8))
do {
    let data = try JSONEncoder().encode(simdFloat)
    let decodedObject = try JSONDecoder().decode(simd_float3x3.self, from: data)
    print(decodedObject)  // simd_float3x3([[0.0, 1.0, 2.0], [3.0, 4.0, 5.0], [6.0, 7.0, 8.0]])

} catch {
    print(error)
}