A simple stopwatch in Swift

Stopwatch.swift

import Foundation

/**
*  A really simple timer that I didn't want to call `Timer` because timer means something else in Foundation.
*/
@objc class Stopwatch: NSObject {
    private var startTime: NSDate?
    
    var isRunning: Bool {
        return startTime != nil
    };
    
    func start() {
        startTime = NSDate.date()
    }
    
    func stop() -> NSTimeInterval {
        if let time = startTime {
            startTime = nil
            
            return NSDate.date().timeIntervalSinceDate(time)
        }
        else {
            return 0
        }
    }
}

Nice!

Swift 3:

@objc class Stopwatch: NSObject {
private var startTime: NSDate?

var isRunning: Bool {
    return startTime != nil
};

func start() {
    startTime = Date() as NSDate
}

func stop() -> TimeInterval {
    if let time = startTime {
        startTime = nil
        
        let endDate = Date() as NSDate
        return endDate.timeIntervalSince(time as Date)
    }
    else {
        return 0
    }
}
}