swift4 - Make UIColor Codable

Question

struct Task: Codable {
    var content: String
    var deadline: Date
    var color: UIColor
...
}

There are warnings saying "Type 'Task' does not conform to protocol 'Decodable'" and "Type 'Task' does not conform to protocol 'Encodable'". I searched and found that this is because UIColor does not conform to Codable. But I have no idea how to fix that. So...

How to make UIColor Codable?

Answer 1

If you care only about the 4 color components this is a simple solution using a wrapper struct

struct Color : Codable {
    var red : CGFloat = 0.0, green: CGFloat = 0.0, blue: CGFloat = 0.0, alpha: CGFloat = 0.0

    var uiColor : UIColor {
        return UIColor(red: red, green: green, blue: blue, alpha: alpha)
    }

    init(uiColor : UIColor) {
        uiColor.getRed(&red, green: &green, blue: &blue, alpha: &alpha)
    }
}

In this case you have to write a custom initializer to convert the 4 color components from Color to UIColor and vice versa.

struct Task: Codable {

    private enum CodingKeys: String, CodingKey { case content, deadline, color }

    var content: String
    var deadline: Date
    var color : UIColor

    init(content: String, deadline: Date, color : UIColor) {
        self.content = content
        self.deadline = deadline
        self.color = color
    }

   init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        content = try container.decode(String.self, forKey: .content)
        deadline = try container.decode(Date.self, forKey: .deadline)
        color = try container.decode(Color.self, forKey: .color).uiColor
    }

    public func encode(to encoder: Encoder) throws {
        var container = encoder.container(keyedBy: CodingKeys.self)
        try container.encode(content, forKey: .content)
        try container.encode(deadline, forKey: .deadline)
        try container.encode(Color(uiColor: color), forKey: .color)
    }
}

Now you can encode and decode UIColor

let task = Task(content: "Foo", deadline: Date(), color: .orange)
do {
    let data = try JSONEncoder().encode(task)
    print(String(data: data, encoding: .utf8)!)
    let newTask = try JSONDecoder().decode(Task.self, from: data)
    print(newTask)
} catch {  print(error) }