Worried..? Not Today..😎 Now that is here, sooner or later we’ll have to migrate our code. Swift 4 Earlier, when arrived, migration seemed to be a tedious task ⚔️. contained some very major API changes. Of course, provided us with the migrator tool to reduce manual overhead, but as we say there is always some loophole left no matter how hard we try. Even after the swift migrator tool did most of it, but still there was a lot of work left to be done by the developer himself 😰. Swift 3 Swift 3 Apple Now again we have to deal with one more such migration 🤢. But don’t worry, this time its not that difficult like before. There are not many major changes in the already existing APIs. Although, some new APIs are definitely added to the frameworks, but that’s not our concern right now. Our only focus at this moment is what changes we need to make in our code that uses the changed APIs. Let’s Begin..!!! 🚀 Let’s have a look on the major errors and warnings that might appear while migrating your code to Swift 4.0. 1. @objc inference Before Swift 4, the compiler made some . For example, if one subclassed from NSObject, the compiler created Objective-C entry points for all methods in such classes. The mechanism is called @objc inference. Swift declarations automatically available to Objective-C because it is costly to generate all those Objective-C entry points. When “Swift 3 @objc Inference” setting is set to “On”, it allows the old code to work. However, it will show deprecation warnings that need to be addressed. It is recommended to “fix” these warnings and , which is the default for new Swift projects. In Swift 4, such automatic @objc inference is deprecated switch the setting to “Default” The issue that I faced was with the _Selectors._😐 A selector expression lets you access the selector used to refer to a method or to a property’s getter or setter in Objective-C. The and must be a reference to a method or a property that is available in the Objective-C runtime. method name property name In short, in interact with APIs and hence require an inference. Earlier it was automatically handled by the compiler. But in , you need to define it explicitly. selectors Swift Objective-C @objc Swift 4 In Swift 3.2 😬 In Swift 4.0 — use the Fix suggested by Swift compiler and it will add @objc inference to the selector method. 2. Declarations from/in extensions cannot be overridden yet In , there was no restriction on method overriding from or in a . But in , you just cannot (it might be available in near future). Swift 3 class extension Swift 4 yet add new functionality to an existing class, structure, enumeration, or protocol type. This includes the ability to extend types for which you do not have access to the original source code Extensions Extensions can add new functionality to a type, but they cannot override existing functionality. While migrating to , you’ll get 🙈 if you have used extensions to override methods. Swift 4 compile-time errors In Swift 3.2 isValid() is defined in BaseCell’s extension isBlank() is defined in BaseCell original source code and overridden in SampleCell’s extension In Swift 4.0 — just move the overridden methods’ definition to original class source code 🎯 3. NSAttributedString attributes’ key names A very straight forward change is introduced in API — the corresponding to the of an will now be referred using an NSAttributedString key names attributes attributed string enum NSAttributedStringKey. Example: will now be referred as NSFontAttributeName NSAttributedStringKey.font will now be referred as etc_._ NSForegroundColorAttributeName NSAttributedStringKey.foregroundColor In Swift 3.2 😅 In Swift 4.0 — simply use the Fix suggested by Swift compiler and it will do all the work for you Promotions Don’t forget to read my other articles: Everything you’ve always wanted to know about notifications in iOS Drag It & Drop It in Collection & Table — iOS 11 Everything about Codable in Swift 4 Color it with GRADIENTS — iOS All you need to know about Today Extensions (Widget) in iOS 10 UICollectionViewCell selection made easy..!! I will update the article as I proceed further with the migration. Watch this space for more on . Swift 4 migration Feel free to leave comments in case you have any doubts. 🙂🙃
