Decoding array of arrays

[oronbz]

Hi,
I have an issue decoding array of arrays,
how would you write a decode function which decode a JSON like this:

"summary": {
  "items": [[0], [1], [2]]
}

I've tried writing a struct like this:

struct Summary {
  let items: [[Int]]
}

and an extension:

extension Summary: Decodable {
  static func decode(_ e: Extractor) throws -> Summary {
    return try Summary(items: e <|| "items")
  }
}

but I'm getting an error:
Type '[Int]' does not conform to protocol 'Decodable'

I know the JSON could be built better but this is what I'm getting from the server and this is what I have to decode.

Thanks,
Oron

[toshi0383]

I ended up writing this code.

infix operator <||<|| : MultiplicationPrecedence

/// - Throws: DecodeError or an arbitrary ErrorType
public func <||<|| <T: Decodable>(e: Extractor, keyPath: KeyPath) throws -> [[T]] {
    let json: [String: Any] = try castOrFail(e.rawValue)
    let array: [Any] = try castOrFail(json[keyPath.components.joined(separator: ".")])
    return try array.map { c -> [T] in
        return try castOrFail(c)
    }
}

I would add this to your App, rather than to Himotoki. I think it's better to keep the core code small.

I also needed to add Optional version of castOrFail to suppress the warning that says Expression implicitly coerced from 'Any?' to Any.

public func castOrFail<T>(_ any: Any?) throws -> T {
    guard let result = any as? T else {
        throw typeMismatch("\(T.self)", actual: any)
    }
    return result
}

So now you can do this.

extension Summary: Decodable {
  static func decode(_ e: Extractor) throws -> Summary {
    return try Summary(items: e <||<|| "items")
  }
}

[ikesyo]

Sorry for the late response, and thanks to @toshi0383 for sharing your way!

Seems that this is a duplicate of #149 and I'd rather write something like this: #149 (comment).

[toshi0383]

Wow, that looks neat😮

[oronbz]

Thank you both guys, I'll have a look at both solutions