swift-protocols

Overview: I have a protocol P1 which provides a default implementation of one of the Objective-C optional functions. When I provide a default implementation of the optional function there is a warning Compiler Warning: Non-'@objc' method 'presentationController(_:viewControllerForAdaptivePresentationStyle:)' does not satisfy optional requirement of '@objc' protocol 'UIAdaptivePresentationControllerDelegate' Version: Swift: 3 Xcode: 8 (public release) Attempts made: Tried adding @objc but doesn't help Question: How do I resolved this ? Is there a work around ? Code: @objc protocol P1 :

Is it possible in Swift? If not then is there a workaround to do it? 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 structs, enums and non- NSObject classes to it. Also, this means you can take advantage of powerful generics system. You can always be sure that all requirements are met when

I am trying to create a Dictionary (actually a HashSet ) keyed on a custom protocol in Swift, but it is giving me the error in the title: Protocol 'myProtocol' can only be used as a generic constraint because it has Self or associated type requirements and I can't make heads nor tails of it. protocol Observing: Hashable { } var observers = HashSet<Observing>() Protocol Observing inherits from protocol Hashable , which in turn inherits from protocol Equatable . Protocol Equatable has the following requirement: func ==(lhs: Self, rhs: Self) -> Bool And a protocol that contains Self somewhere

weak references don't seem to work in Swift unless a protocol is declared as @objc , which I don't want in a pure Swift app. This code gives a compile error ( weak cannot be applied to non-class type MyClassDelegate ): class MyClass { weak var delegate: MyClassDelegate? } protocol MyClassDelegate { } I need to prefix the protocol with @objc , then it works. Question: What is the 'pure' Swift way to accomplish a weak delegate ? flainez You need to declare the type of the protocol as class . protocol ProtocolNameDelegate: class { // Protocol stuff goes here } class SomeClass { weak var delegate:

In Swift I can explicitly set the type of a variable by declaring it as follows: var object: TYPE_NAME If we want to take it a step further and declare a variable that conforms to multiple protocols we can use the protocol declarative: var object: protocol<ProtocolOne,ProtocolTwo>//etc What if I would like to declare an object that conforms to one or more protocols and is also of a specific base class type? The Objective-C equivalent would look like this: NSSomething<ABCProtocolOne,ABCProtocolTwo> * object = ...; In Swift I would expect it to look like this: var object: TYPE_NAME,ProtocolOne/