swift-protocols

问题 I have a protocol like so public protocol FooProtocol { associatedType someType func doFoo(fooObject:someType) -> Void } I have a class that implements this protocol public class Foo<T> : FooProtocol { private let _doFoo : (T) -> Void init<P : FooProtocol where P.someType == T>(_dep : P) { _doFoo = _dep.doFoo } public func doFoo(fooObject: T) { _doFoo(fooObject) } } Everything upto here looks good to me, Now in another class I implement the FooProtocol with someType = MyType , then when I try

问题 I'm trying to build a generic UITableViewController subclass in Swift that will accommodate any number of different kinds of table view cells without having internal knowledge of any of them. To do this I'm trying to use protocols for my models and for my table view cells. The protocol for the models will return which cell class I should be going to, and the protocol for the cells will return answers to questions like what the height of the cell should be for a given model. But I'm having a

问题 This question already has an answer here : EXC_BAD_ACCESS Using IBInspectable (1 answer) Closed 2 years ago . I want to have a default property of UIImageView , which would be isFlipped . I am able to do it by subclassing UIImageView and adding one property isFlipped . But I want to user protocol and extensions for this , but it is crashing after sometime. Below is my code. How can I use it in right way? Thanks import Foundation import UIKit protocol FlipImage { var isFlipped: Bool { get set

问题 The following code doesn't compile: enum Occupation: String { case designer = "Designer" case engineer = "Engineer" } public struct SteveJobs: Codable { let name: String let occupation: Occupation } On the other hand, it should compile since the Occupation is represented as a String which is Codable . Why can't I use enum with raw value in Codable structs? In particular, why automatic conformance isn't working in such a case. 回答1: Automatic Codable synthesis is “opt-in,” i.e. you have to

问题 I have a protocol that I've created (in Swift 4.2), and one of its requirements is a property that is of the same type as the protocol itself. As an example, I have a protocol defined like so: protocol A { var a: A? { get set } } I have several Models that conform to this protocol: class Model1: A { var a: A? } class Model2: A { var a: A? } For one of my models, I need to satisfy the protocol requirement by being more specific for the property defined by variable a (i.e. the variable with the

问题 I found the following example on the web about using generics together with protocols, however I don't understand why do we need generics at all, when all we need is to use a protocol. We define a protocol: protocol Healthy { mutating func setAlive(status: Bool) var health: Int { get } } And then a function using a generic adotping that protocol func check<T:Healthy>(inout object: T) { if (object.health <= 0) { object.setAlive(false) } } I've changed the code as below and everything is still

问题 Class A provides a string value. Class B has two members of A type inside itself, and provide a computed property "v" to choose one of them. class A { var value: String init(value: String) { self.value = value } } class B { var v1: A? var v2: A = A(value: "2") private var v: A { return v1 ?? v2 } var value: String { get { return v.value } set { v.value = newValue } } } This code is simple and it works. Since both the A and B have a member "value", I make it a protocol like this: protocol

问题 Recently I have been developing multiple heavily protocol-oriented application frameworks with Swift and noticed a few (seemingly) odd behaviors with static functions in protocol extensions, specifically where the extension functions are invoked from metatypes. The way I initially discovered these behaviors was in troubleshooting a bug where the type of an object changed in a seemingly impossible way. I traced the problem down and eventually determined that it is because in a static function,

问题 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

问题 So I wrote a simple protocol: protocol PopupMessageType{ var cancelButton: UIButton {get set} func cancel() } and have a customView: class XYZMessageView: UIView, PopupMessageType { ... } and then I currently have: class PopUpViewController: UIViewController { //code... var messageView : CCPopupMessageView! private func setupUI(){ view.addSubview(messageView) } } But what I want to do is: class PopUpViewController: UIViewController { //code... var messageView : PopupMessageType! private func