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Static variable vs Class variable in Swift

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How Static properties differs to usual properties ? Used to create type properties with either let or var. These are shared between all objects of a class.  During class loading time, a single memory location allocated for the property if we declared as static. Static property belongs to a class (or struct) Type rather than Instance of class (or struct). Hence it also called  Type Properties What if we declare "static var" ? Since it's a variable, we can change it in future even after initialised. When we change the value of the static variable property, that property is now changed in all future instances. What if we declare "static let" ? static let instance : Singleton = Singleton() Since it's constant, we cannot change once initialised. Its value will remain same even if we share among all the instance or object of a class or struct. Useful to adopt singleton pattern. How class variables differ static variables ? It dif...
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Reference Type vs Value Type

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How do we get to know reference type ?  In Swift , a class or closure or function can be Reference Type. In Objc, everything inherited from NSObject represents Reference Type. How do we get to know value type ?  In Swift, we have Structures, Enums and Tuples, along with Int, Double, String, Array, Dictionary, Set as well. In Objc, Number literals like NSInteger, C structures like CGPoint. When to use Reference type ? Comparing two objects those shares the same memory address (aka === ) When you want to create a shared and mutable state When to use Value Type ? Comparing instance data with == makes sense.  You want copies to have independent state.  The data will be used in code across multiple threads. How about memory Allocation ?  Heap memory for reference types.  Stack for Value types. Linked to similar questions : Struct vs Class String vs NSString (Source-Internet)
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Swift Delhi Meetup - Chapter 23

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I should thank Swift Delhi & Nykaa folks for hosting meetup on 25th Jan at Nykaa, Gurugram. Worth spending every minute with various developers from iOS community. We had 5 interesting sessions on app development standards, exploring & adopting new frameworks. Here I noted few take away points on each talks which could be useful for you. Below are talks lined up for the chapter. ------------------------------------------------------------------------------------------------ 1. Leveraging the power of silent push notifications Speaker: Yogesh Suthar, Sr. Software Engineer @Nykaa https://in.linkedin.com/in/yogesh-suthar Leveraging the power of silent push notifications for business growth, user retention and better user experience. Understanding the working of silent push flow, hacks and practical use-cases. 2. Distributing private frameworks using cocoapods Speaker: Sagar Rana, Sr. Software Engineer @Nykaa https://www.linkedin.com/in/ranasagar While working on...
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Implementing autocompletion OTP field in iOS

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Long waiting is over. !!  iOS 12 brings Autofill for OTP text field which is close to Android provided a decade back. Previously in iOS we used to toggle between OTP text screen and message inbox.  Which was hard to remember and time consuming resulting a bad user experience. Personally, I have been asked from the client/customer couple of times to implement autocompletion for OTP field and took me a lot of time to convey that it is not possible in iOS. Why Autofill was not possible previously?  We all know that Apple gives at most care for user privacy. When we see iOS architecture, each individual app is like a separate island. There is no inter-app bridge between apps (exception for Keychain and URLSchemes APIs which gives very limited scope). Thus we cannot read message content from inbox. Where to start Autofilling? First of all, the target SMS need to have the OTP Code with prefix string "Code" or "Passcode"on its message content. Beware of OTP c...
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Animating label text update - choosing a better way

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Recently I published a countdown app .  At one point of development - I have to show a timer on a UILabel which ticks on each seconds. As usual I started  setting text to a label object - self .timerLabel.text = someString Easy piece of cake right !?   But wait ... it won't take much user attention when timer ticks on every seconds. So I decided to make use of a simple animation while label gets text update. I found there are dozens of ways to animate a label. In this short article, I listed 3 best way you can animate text on a label. ( Spoiler Alert 👀- I decided to go with 3rd option)  1. Fade In - Fade out animation : CATransition class has got transition type `fade`. With timing function of CATransition - I was able to see the below result. let animation: CATransition = CATransition () animation.timingFunction = CAMediaTimingFunction (name: CAMediaTimingFunctionName .easeInEaseOut) animation.type = CATransitionType .fade animation.subtype = C...
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Cached Async Image in SwiftUI

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 SwiftUI’s AsyncImage is handy, but every time your view appears, it refetches the image—leading to flicker, delays, and unnecessary network use. What if you could fetch once, then reuse instantly? That's exactly what the Cached Async Image  delivers: a memory-powered caching layer that keeps SwiftUI image loading smooth, snappy, and resilient. First a simple in-memory cache without disk persistence. This will be thread-safe and auto-purges under memory pressure. A Singleton wrapping NSCache for URL → UIImage caching as follows : final class ImageCache {   static let shared = ImageCache()   private init() {}   private let cache = NSCache<NSURL, UIImage>()   func image(for url: URL) -> UIImage? {     cache.object(forKey: url as NSURL)   }   func insertImage(_ image: UIImage?, for url: URL) {     guard let image else { return }     cache.setObject(image, forKey: url as NSURL)   }   func clearAll() { ...
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Prevent Navigationbar or Tabbar overlapping Subview - solved for Card view

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Recently, I started with a Card view added as a subview of UIView in a view-controller. When a view controller created along subviews, it tends to use entire screen bounds and also slips behind Tab bar or Navigation bar. In my current situation, it's second case. Casually new iOS developers will write a patch by additional value for coordinate y and subtracting bar height from its size. A lot of them posted in SO threads too : How to prevent UINavigationBar from covering top of view? View got hidden below UINavigationBar iOS 7 Navigation Bar covers some part of view at Top So, how I got solved ? self.edgesForExtendedLayout = [] This  will avoid all subviews in a view controller get behind any bars. Read full apple  documentation on here. Full Source code below :  //Simple view controller where its view layed-out as a card. class WidgetCardViewController : UIViewController { var containerView = UIView () //MARK:- View Controller Life Cyc...
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UICollectionViewCell shows with wrong size on First time - Solved

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We commonly use Collection view where its cell size calculated run time. The flow layout delegate is responsible to return individual cell sizes. BUT in most of the cases, delegate method `collectionView: layout sizeForItem:` expects cell size too early. Before generating actual cell size. extension YourViewController : UICollectionViewDelegateFlowLayout { func collectionView ( _ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize { return CGSize (width: externalWidth, height: externalHeight) } } For instance, if a cell size depends on external view and its frame is not yet ready - results with wrong (or outdated) cell size. Typically happens for the first time view controller laid out all views. You can find similar queries in StackOverflow community : Collection view sizeForItemNotWorking UICollectionViewCell content wrong size on first load How to refresh UICollec...
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