Introduce local extension

gistfile1.txt

//: Introduce Local Extension
/*:
 */

import Foundation

struct DateWrapper {
    private var origDate: Date
    
    init(date: Date) {
        origDate = date
    }
    
    init?(dateString: String) {
        let formatter = DateFormatter()
        formatter.dateFormat = "yyyy-MM-dd hh:mm"
        if let date = formatter.date(from: dateString) {
            origDate = date
        } else {
            return nil
        }
    }
    
    func getPreviousDate() -> Date {
        return Date(timeIntervalSinceNow: -60 * 60 * 24 )
    }
    
    func getNextDate() -> Date {
        return Date(timeIntervalSinceNow: 60 * 60 * 24)
    }
    
    func getYear() -> String {
        return generateDateFormatter(partType: "yyyy").string(from: origDate)
    }
    
    func getMonth() -> String {
        return generateDateFormatter(partType: "MM").string(from: origDate)
    }
    
    func getDays() -> String {
        return generateDateFormatter(partType: "dd").string(from: origDate)
    }
    
    private func generateDateFormatter(partType: String) -> DateFormatter {
        let formatter = DateFormatter()
        formatter.dateFormat = partType
        return formatter
    }
}

let dateWrapper = DateWrapper(date: Date())
let previousDate = dateWrapper.getPreviousDate()
let nextDate = dateWrapper.getNextDate()
let year = dateWrapper.getYear()
let month = dateWrapper.getMonth()