extension-extending-optional.swift

// Optionable protocol exposes the subset of functionality required for flatten definition
protocol Optionable {
    typealias Wrapped
    var value: Wrapped? { get }
}

// extension for Optional provides the implementations for Optional enum
extension Optional : Optionable {
    var value: Wrapped? { get { return self } }
}

extension SequenceType where Self.Generator.Element : Optionable {
    func flatten() -> [Self.Generator.Element.Wrapped] {
        return self.filter({ $0.value != nil }).map({ $0.value! })
    }
}

let sequence = [Optional.Some(1), Optional.Some(2), Optional.None, Optional.Some(3), Optional.Some(4)]

let flat = sequence.flatten()

flat // [1, 2, 3, 4]

nice man

Updated Syntax:

protocol Optionable {
    associatedtype Wrapped
    var value: Wrapped? { get }
}

// extension for Optional provides the implementations for Optional enum 
extension Optional : Optionable {
    var value: Wrapped? { return self  }
}

extension SequenceType where Self.Generator.Element : Optionable {
    func flatten() -> [Self.Generator.Element.Wrapped] {
        return flatMap { $0.value } 
    }
}

extension LazySequenceProtocol where Self.Iterator.Element : Optionable {
    func flatten() -> [Self.Iterator.Element.Wrapped] {
        return compactMap { $0.value }
    }
}

// MARK: - Helpful methods for flattening dictionary
//  Created by Alexander Volkov on 3/14/19.
//  Copyright (c) 2019 Alexander Volkov. All rights reserved.
extension Dictionary where Value: Optionable {

    /// flatten dictionary
    public func flatten() -> [Key: Value.Wrapped] {
        return self.filter({ (k, v) in
            return v.value != nil
        }).mapValues({$0.value!})
    }
}

For example:

var userId: String? = ..
var query: String? = ..
let parameters: [String: Any?] = [
            "query": query,
            "userId": userId
        ]
parameters.flatten() // [String: Any]