Reloading/inserting Dynamic Height cells and keeping Scroll position

For an upcoming app I had to insert Dynamic Height cells while keeping the tableView offset -scrolling position- constant. This would typically be a trivial issue, but given that when using Dynamic Height cells nor the contentSize nor the offset can be trusted it’s a bit more tricky than it seems… What I was trying …

Dealing with UIGraphics ImageContext ‘Memory Leaks’

Here’s the code to change the image size of an image in iOS so that then it can be saved with smaller footprint: let rect = CGRect(x: 0, y: 0, width: newSize.width, height: newSize.height)          // Actually do the resizing to the rect using the ImageContext stuff UIGraphicsBeginImageContextWithOptions(newSize, false, 1.0) image.draw(in: rect) …

Pre-Scrolling a Table to a specific cell at load

Although that’s something that appears fairly easy, the truth -for me at least-, is that scrolling a UITableView to a specific cell every time you load it may prove tricky.  In the app I’m working on I implement it in the following way: every time a view appeared I assess if the top visible row …

Find the right value in an Array, or in an Array of Dictionaries

From time to time I discover a new way of coding something that significantly improves readability & minimizes how much I need to code.  Here’s one of such latest discoveries. Typically to find a value in an array (or in an array of dictionaries) with a specific condition I would do a for loop with …

Inserting cells at the top of a UITableView with no scrolling

If you would like your table to be refreshed “ala Twitter”, with new data being added on top, here’s a quick an easy way to do it for iOS:  func updateTableViewAfterAdditionInNewArray(){         //Get new feeds and check if counts are different         let countOfAddedItems = oldArray.count – newArray.count    …

Multi Thread access to shared Variables – Swift 4 Concurrency

Working with background threads really helps improve the app responsiveness & the overall user experience. But, and it’s a big but, you have to be aware of multithread access conflicts.  If you access/modify the same variable from multiple threads you’re prone to non-reproducible -seemingly random- crashes. How to Detect Conflicts? To help you find where …

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.    Marc

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 {             …