swift-extensions

How to make extension for multiple classes Swift

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You could make a protocol and extend it. Something like: protocol Animations { func animateHidden(flag: Bool) } extension Animations { func animateHidden(flag: Bool) { // some code } } extension UILabel: Animations {} extension UIImageView: Animations {} Your method will be available for the extended classes: let l = UILabel() l.animateHidden(false) let i = UIImageView() … Read more

what is ‘where self’ in protocol extension

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That syntax is: https://developer.apple.com/library/content/documentation/Swift/Conceptual/Swift_Programming_Language/Protocols.html#//apple_ref/doc/uid/TP40014097-CH25-ID521 Consider: protocol Meh { func doSomething() } // Extend protocol Meh, where `Self` is of type `UIViewController` // func blah() will only exist for classes that inherit `UIViewController`. // In fact, this entire extension only exists for `UIViewController` subclasses. extension Meh where Self: UIViewController { func blah() { print(“Blah”) } func … Read more

Swift 2 Error using mutating function in Protocol extension “Cannot use mutating member on immutable value: ‘self’ is immutable

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The problem is that, in the protocol you mark the function as mutating, which you need to do if you want to use the protocol on a struct. However, the self that is passed to testFunc is immutable (it’s a reference to a instance of the class) and that is tripping up the compiler. This … Read more

Set (Collection) – Insert multiple elements

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It was pointed out in the comments under the question, but I’d like to clearly state that there is a method for that very same purpose: mutating func formUnion<S>(_ other: S) where Element == S.Element, S : Sequence Usage: var attendees: Set = [“Alicia”, “Bethany”, “Diana”] let visitors = [“Diana”, “Marcia”, “Nathaniel”] attendees.formUnion(visitors) print(attendees) // … Read more

Creating an extension to filter nils from an Array in Swift

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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

How does one declare optional methods in a Swift protocol?

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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

How to define initializers in a protocol extension?

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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

Extend array types using where clause in Swift

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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

How to create swift class for category?

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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