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
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
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
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
I see no reason why the compiler shouldn’t be able to resolve this function call, therefore I would consider it a bug (it has already been filed – see SR-2450). It seems to occur whenever attempting to call a top-level function with the same name, but unambiguously different signature to a method or property that’s … Read more
Similar as in Using ‘self’ in class extension functions in Swift, you can define a generic helper method which infers the type of self from the calling context: extension UIViewController { class func instantiateFromStoryboard(storyboardName: String, storyboardId: String) -> Self { return instantiateFromStoryboardHelper(storyboardName, storyboardId: storyboardId) } private class func instantiateFromStoryboardHelper<T>(storyboardName: String, storyboardId: String) -> T { … 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