Convenience methods for "date arithmetic" in easy to read and use formats

Date+Intervals.swift

//
//  Date+Intervals.swift
//
//  Created by Zhendryk on 11/1/18.
//  Copyright © 2018 Zhendryk. All rights reserved.
//

import Foundation

extension Date {
    
    func getAmountOfTime(from date: Date, period: Calendar.Component) -> Int {
        switch period {
        case .year:
            return years(from: date)
        case .month:
            return months(from: date)
        case .weekOfMonth:
            return weeks(from: date)
        case .day:
            return days(from: date)
        case .hour:
            return hours(from: date)
        case .minute:
            return minutes(from: date)
        case .second:
            return seconds(from: date)
        case.nanosecond:
            return nanoseconds(from: date)
        default:
            return 0
        }
    }
    
    /// Returns the amount of years from another date
    func years(from date: Date) -> Int {
        return Calendar.current.dateComponents([.year], from: date, to: self).year ?? 0
    }
    /// Returns the amount of months from another date
    func months(from date: Date) -> Int {
        return Calendar.current.dateComponents([.month], from: date, to: self).month ?? 0
    }
    /// Returns the amount of weeks from another date
    func weeks(from date: Date) -> Int {
        return Calendar.current.dateComponents([.weekOfMonth], from: date, to: self).weekOfMonth ?? 0
    }
    /// Returns the amount of days from another date
    func days(from date: Date) -> Int {
        return Calendar.current.dateComponents([.day], from: date, to: self).day ?? 0
    }
    /// Returns the amount of hours from another date
    func hours(from date: Date) -> Int {
        return Calendar.current.dateComponents([.hour], from: date, to: self).hour ?? 0
    }
    /// Returns the amount of minutes from another date
    func minutes(from date: Date) -> Int {
        return Calendar.current.dateComponents([.minute], from: date, to: self).minute ?? 0
    }
    /// Returns the amount of seconds from another date
    func seconds(from date: Date) -> Int {
        return Calendar.current.dateComponents([.second], from: date, to: self).second ?? 0
    }
    /// Returns the amount of nanoseconds from another date
    func nanoseconds(from date: Date) -> Int {
        return Calendar.current.dateComponents([.nanosecond], from: date, to: self).nanosecond ?? 0
    }
    /// Returns the custom time interval description from another date
    func offset(from date: Date) -> String {
        if years(from: date)   > 0 { return "\(years(from: date))y"   }
        if months(from: date)  > 0 { return "\(months(from: date))M"  }
        if weeks(from: date)   > 0 { return "\(weeks(from: date))w"   }
        if days(from: date)    > 0 { return "\(days(from: date))d"    }
        if hours(from: date)   > 0 { return "\(hours(from: date))h"   }
        if minutes(from: date) > 0 { return "\(minutes(from: date))m" }
        if seconds(from: date) > 0 { return "\(seconds(from: date))s" }
        if nanoseconds(from: date) > 0 { return "\(nanoseconds(from: date))ns" }
        return ""
    }

    func isBetween(date date1: Date, andDate date2: Date) -> Bool {
        return date1.compare(self).rawValue * self.compare(date2).rawValue >= 0
    }
}