As of Swift 2.0, you don’t need to write your own extension to filter nil values from an Array, you can use flatMap, which flattens the Array and filters nils: let optionals : [String?] = [“a”, “b”, nil, “d”] let nonOptionals = optionals.flatMap{$0} print(nonOptionals) Prints: [a, b, d] Note: There are 2 flatMap functions: One … Read more
As you can see this doesn’t work under these circumstances because when compiling, one has to make sure that all properties are initialized before using the struct/enum/class. You can make another initializer a requirement so the compiler knows that all properties are initialized: protocol Car { var wheels : Int { get set } // … Read more
If you want to extend only array with specific type. You should extend _ArrayType protocol. extension _ArrayType where Generator.Element == Int { func doSomething() { … } } If you extend Array you can only make sure your element is conformed some protocol else. i.e: extension Array where Element: Equatable { func doSomething() { … … Read more
In Swift, you can use Extensions to add new functionality to existing classes, structs and enumeration types. They differ from Objective-C categories in a few ways, mainly: They aren’t named You don’t need to import an Extension explicitly. If you define an extension to add new functionality to an existing type, the new functionality will … Read more
In Swift 3.1 you can add an extension to optional values as well: extension Optional where Wrapped == String { var isBlank: Bool { return self?.isBlank ?? true } }
You can write a Swift extension and use it in Objective-C code. Tested with Xcode 6.1.1. All you need to do is: create your extension in Swift (@objc annotation needed since Swift 4.0.3) #import “ProjectTarget-Swift.h” in your Objective-C class (where “ProjectTarget” represents the XCode target the Swift extension is associated with) call the methods from … Read more
Extensions cannot/should not override. It is not possible to override functionality (like properties or methods) in extensions as documented in Apple’s Swift Guide. Extensions can add new functionality to a type, but they cannot override existing functionality. Swift Developer Guide The compiler is allowing you to override in the extension for compatibility with Objective-C. But … Read more
1. Using default implementations (preferred). protocol MyProtocol { func doSomething() } extension MyProtocol { func doSomething() { /* return a default value or just leave empty */ } } struct MyStruct: MyProtocol { /* no compile error */ } Advantages No Objective-C runtime is involved (well, no explicitly at least). This means you can conform … Read more