Decodable instantiation from an asset catalog Data Set to help with SwiftUI Previews

PreviewHelpers.swift

import UIKit

extension NSDataAsset {
    /// Load a data asset from a catalog and try decoding it to a specific Decodable type
    /// - Returns: An optional instance of type T decoded from the named data asset
    /// Usage: `NSDataAsset.decode(DocodableThing.self, asset: "my thing")`
    public static func decode<T>(_ type: T.Type, asset name: String) -> T? where T: Decodable {
        guard let asset = Self(name: name) else { return nil }
        return try? JSONDecoder().decode(T.self, from: asset.data)
    }
}

extension Decodable {
    /// Optional initializer from JSON data stored in an asset catalog
    /// - Parameter name: the string name of an asset in a catalog
    /// - Returns: Optional instance of a decodable from the JSON data stored in the asset catalog
    /// Usage: `DecodableThing(asset: "my thing")`
    public init?(asset name: String) {
        guard let me = NSDataAsset.decode(Self.self, asset: name) else { return nil }
        self = me
    }
}