Swift: determine whether optional String, NSString, or collection is nil or empty

isNilOrEmpty.swift

import Foundation

/**
    Determine whether Optional collection is nil or an empty collection

    :param: collection Optional collection
    :returns: true if collection is nil or if it is an empty collection, false otherwise
*/
public func isNilOrEmpty<C: CollectionType>(collection: C?) -> C? {
    switch collection {
        case .Some(let nonNilCollection): return count(nonNilCollection) > 0 ? nonNilCollection : nil
        default:                          return nil
    }
}

/**
    Determine whether Optional NSString is nil or an empty string

    :param: string Optional NSString
    :returns: true if string is nil or if it is an empty string, false otherwise
*/
public func isNilOrEmpty(string: NSString?) -> Bool {
    switch string {
        case .Some(let nonNilString): return nonNilString.length > 0 ? nonNilString : nil
        default:                      return nil
    }
}


// String examples (note that a String is a collection)

let nilString: String? = nil
isNilOrEmpty(nilString)

let emptyString: String? = ""
isNilOrEmpty(emptyString)

let nonEmptyString: String? = "Hello, world!"
isNilOrEmpty(nonEmptyString)


// NSString examples

let nilNSString: NSString? = nil
isNilOrEmpty(nilNSString)

let emptyNSString: NSString? = ""
isNilOrEmpty(emptyNSString)

let nonEmptyNSString: NSString? = "Hello, world!"
isNilOrEmpty(nonEmptyNSString)


// Array examples

let nilArray: [Int]? = nil
isNilOrEmpty(nilString)

let emptyArray: [Int]? = []
isNilOrEmpty(emptyArray)

let nonEmptyArray: [Int]? = [0, 1, 2, 3]
isNilOrEmpty(nonEmptyArray)