Random numbers in Swift

Swift 4.2 has introduced a native random number API in the standard library, making it cross platform. 

Int.random(in: 1...1000) // → 691
Double.random(in: 0..<1) // → 0.8741555749903935
UInt32.random(in: 0xD800...0xDFFF) // → 55666

Read more in the great article from Ole Begemann, worth a read



Resize NSImage Proportionally (Swift)

I wanted a simple function to resize an image to a desired height, while keeping proportions. Here’s what I came up with (based on Marco implementation):

extension NSImage {


    func resizedImageTo(sourceImage: NSImage, newSize: NSSize) -> NSImage?{

        if sourceImage.isValid == false {

            return nil


        let representation = NSBitmapImageRep(bitmapDataPlanes: nil, pixelsWide: Int(newSize.width), pixelsHigh: Int(newSize.height), bitsPerSample: 8, samplesPerPixel: 4, hasAlpha: true, isPlanar: false, colorSpaceName: .calibratedRGB, bytesPerRow: 0, bitsPerPixel: 0)

        representation?.size = newSize



        NSGraphicsContext.current = NSGraphicsContext.init(bitmapImageRep: representation!)

        sourceImage.draw(in: NSRect(x: 0, y: 0, width: newSize.width, height: newSize.height), from: NSZeroRect, operation: .copy, fraction: 1.0)



        let newImage = NSImage(size: newSize)



        return newImage






Questions / comments / suggestions? I’m at @MarcMasVi 


Updated after I discovered the great implementation Marco Arment suggested. 

Open links in the Background

Here’s a quick tip on how to open a URL in the background or foreground depending on a user-set preference. 

if(openInBackgroundPreferenceSet == true){ 
                 NSWorkspace.shared.open([linkToOpen], withAppBundleIdentifier: nil, options: NSWorkspace.LaunchOptions.withoutActivation, additionalEventParamDescriptor: nil, launchIdentifiers: nil)


Questions / comments? I’m at @MarcMasVi 



Denarius 1.6 & the slippery bug

This last couple of months I’ve been hard at work on two new projects, the first of which will be released fairly soon! But, today I wanted to write about something else: CoreData Concurrency.

Since the release of Denarius about a year ago I’ve been regularly improving the personal finance app with new features and, of course, bug fixes. However there was this one bug that kept popping up in crash logs but that I was unable to track down. I knew it had something to do with Core Data but that’s the extend of it. 

CoreData in Denarius is implemented with two Managed Object Context, one of them being the background one for complex tasks and a second one for standard operation (as explained in this post).  So, everything was supposedly working as intended. 

However, after way too many hours I saw what was going on: I was doing a change in the main thread with information computed on the background thread… So, how did I solve it? Using objectID of course, the only safe way to transfer objects between threads. 

So instead of:

mainThreadObject.attributeX = computedThreadObjectInBackgroundQueue.attributeX

Now I had (and remember this piece of code is being executed in the background):

let transactionObjectId = mainThreadObject1.objectID
let typeObjectId = computedThreadObject2InBackgroundQueue.objectID
DispatchQueue.main.async { //Here I’m calling the main thread and push the complex background computation to the right object
      (self.managedObjectContext.object(with: transactionObjectId) as! object1).attributeX = (self.managedObjectContext.object(with: typeObjectId) as! object2).attributeX


A bit longer, but did the trick! This improvement will ship very soon with the new Denarius 1.6 release. 

Questions / comments? I’m at @MarcMasVi