The Objective-C language is based upon selectors. A selector is a message that can be sent to an object or a class. pethydro.org maps. The Unrecognized selector sent to instance is an annoying little error in Xcode. With Swift's syntax improvements this error occurs much less. This chapter covers basic Objective-C skills that help you get started with iOS programming: interfaces, methods, properties, memory. swift-evolution/proposals/pethydro.org In Swift 2, Objective-C selectors are written as string literals (e.g., "insertSubview:aboveSubview:") in the. The @selector attribute indicates which Objective-C selector should be used when calling this method. This attribute needs to be attached to all methods with the. There are two NSObject in Objective-C: NSObject the Because all Objective-C objects implement ObjcObject (the mapping of selectors requires that we know the class or inteface declaration. SEL. Defines an opaque type that represents a method selector. SDKs. iOS +; macOS +; tvOS +; watchOS +. Framework. Objective-C Runtime. You have to be very careful about the method names. In this case, the method name is just " lowercaseString ", not " lowercaseString: " (note the absence of the . A collection of short articles on the core concepts, patterns, and mechanisms in Cocoa programming. Learn how to use Objective-C selectors in Swift in your iOS app. The innovative Apple language allows you to interface with Obj-C in a elegant.