FailableMap.swift

FailableMap.swift

//
//  FailableMap.swift
//
//  Created by Lukas Kubanek on 06/10/15.
//  Copyright © 2015 Lukas Kubanek. All rights reserved.
//

public extension Array {
    
    /// Maps the transform over `self` and if **all** calls return a non-nil result it returns
    /// an Array of the results or `nil` otherwise.
    public func failableMap<T>(transform: Element throws -> T?) rethrows -> [T]? {
        return try reduce([]) { accum, element in
            if let accum = accum, let transfomedElement = try transform(element) {
                return accum + [transfomedElement]
            } else {
                return nil
            }
        }
    }
    
}

public extension Dictionary {
    
    public func failableMapValues<T>(transformValue: Value throws -> T?) rethrows -> [Key: T]? {
        return try reduce([:]) { (accum: [Key: T]?, element: (key: Key, value: Value)) in
            if let accum = accum, let transformedValue = try transformValue(element.value) {
                return accum + [element.key: transformedValue]
            } else {
                return nil
            }
        }
    }
    
}