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Swift blog

建议读一通swift
blog来了解OC与swift不同以及swift版本变动细节

OC id -> Swift Any

瑜,不待手动装箱
令OC API更加灵敏

OC Swift2 Swift3
id AnyObject Any
NSArray * [AnyObject] [Any]
NSDictionary * [NSObject:AnyObject] [AnyHashable:Any]
NSSet * Set<NSObject> Set<AnyHashable>

欲留意的而是swift2不再供隐式转换,因此NS桥接的待你出示转换

Overriding methods and conforming to protocols

取名符合OC的正式,id->Any

// Swift 2
class Foo: NSObject, NSCopying {
    override func isEqual(_ x: AnyObject?) -> Bool { ... }
    func copyWithZone(_ zone: NSZone?) -> AnyObject { ... }
}

// Swift 3
class Foo: NSObject, NSCopying {
    override func isEqual(_ x: Any?) -> Bool { ... }
    func copy(with zone: NSZone?) -> Any { ... }
}

Untyped Collections

隐式桥接不存在了,需要采取as,swift3导入的cocoa接受了Any/AnyHashable,因此对于集合也得以应用[AnyHashable:Any]

// Swift 2
struct State {
    var name: String
    var abbreviation: String
    var population: Int

    var asPropertyList: [NSObject: AnyObject] {
        var result: [NSObject: AnyObject] = [:]//也可以使用NSDictionary
        // Implicit conversions turn String into NSString here…
        result["name"] = self.name
        result["abbreviation"] = self.abbreviation
        // …and Int into NSNumber here.
        result["population"] = self.population
        return result
    }
}

let california = State(name: "California",
                       abbreviation: "CA",
                       population: 39_000_000)
NSNotification(name: "foo", object: nil,
               userInfo: california.asPropertyList)

// Swift 3
struct State {
    var name: String
    var abbreviation: String
    var population: Int

    // Change the dictionary type to [AnyHashable: Any] here...
    var asPropertyList: [AnyHashable: Any] {
        var result: [AnyHashable: Any] = [:]
        // No implicit conversions necessary, since String and Int are subtypes
        // of Any and AnyHashable
        result["name"] = self.name
        result["abbreviation"] = self.abbreviation
        result["population"] = self.population
        return result
    }
}
let california = State(name: "California",
                       abbreviation: "CA",
                       population: 39_000_000)
// ...and you can still use it with Cocoa API here
Notification(name: "foo", object: nil,
             userInfo: california.asPropertyList)

The AnyHashable Type

Any类型可以有另外项目,但是Dictionary、Set需要Hasble,AnyHashble是swift3提出的hashable的超类,任何一个可hash的类且实现了Anyhashble协议,比如String、Int

Explicit Conversion for Unbridged Contexts

在部分限制的场地swift不能够一直桥接C和OC的计划,比如id*,这个时段api将会晤显示UnsafePointer<AnyObject>,此时待as转换,再&

// ObjC
@interface Foo

- (void)updateString:(NSString **)string;
- (void)updateObject:(id *)obj;

@end

// Swift
func interactWith(foo: Foo) -> (String, Any) {
    var string = "string" as NSString // explicit conversion
    foo.updateString(&string) // parameter imports as UnsafeMutablePointer<NSString>
    let finishedString = string as String

    var object = "string" as AnyObject
    foo.updateObject(&object) // parameter imports as UnsafeMutablePointer<AnyObject>
    let finishedObject = object as Any

    return (finishedString, finishedObject)
}

除此以外,OC的合计是类似协议,不能够就此结构体、枚举或另轻量级的通用型遵守OC的商事

AnyObject Member Lookup

Any没有AnyObject的摸索行为艺术,因此无克动态的向Any发送信息,但是AnyObject可以,此时用更换

// Swift 2
func foo(x: NSArray) {
    // Invokes -description by magic AnyObject lookup
    print(x[0].description)
}

// Swift 3
func foo(x: NSArray) {
    // Result of subscript is now Any, needs to be coerced to get method lookup
    print((x[0] as AnyObject).description)//也可以转换到你期望的指定类型as!NSOjbect
}

Swift Value Types in Objective-C

Any可以有所另外的结构体、枚举、元组或者其他的种类,OC的id在swift3等价于any,在swift2中得手动封箱或者转入类,swift3则免待

// Swift 2
struct CreditCard { number: UInt64, expiration: NSDate }

let PaymentMade = "PaymentMade"

// We can't attach CreditCard directly to the notification, since it
// isn't a class, and doesn't bridge.
// Wrap it in a Box class.
class Box<T> {
    let value: T
    init(value: T) { self.value = value }
}

let paymentNotification =
    NSNotification(name: PaymentMade,
                   object: Box(value: CreditCard(number: 1234_0000_0000_0000,
                                                 expiration: NSDate())))


// Swift 3
let PaymentMade = Notification.Name("PaymentMade")

// We can associate the CreditCard value directly with the Notification
let paymentNotification =
    Notification(name: PaymentMade,
                 object: CreditCard(number: 1234_0000_0000_0000,
                                    expiration: Date()))

用小心的凡swift3中对此大规模的布局体类型将会晤桥接作为透明对象要休是cocoa对象,Int、UInt、Double、Bool会桥接为NSNumber,Int8,UInt16虽说单独桥接为透明对象。如果赶上了unrecognized selector sent to _SwiftValue题材,它象征OC尝试唤醒一个办法以swift
值类型上,此时我们用手动管理

swift Any持有任一类包括Optional,尽管OC api要求是nonull
id,Optional在不解包的情事下吧足以作为参数传递,会招runtime
error而无是编译错误。swift3.0.1+Xoce8.1解决了上述问题,为了避免兼容问题,不要因让透明对象为前景之swift可能会见桥接到固定类型

Working with JSON in Swift

JSONSerialization Foundation framework

Extracting Values from JSON

JSONSerialization类方法jsonObject返回Any类型并且扔来很要data不克分析

import Foundation

let data: Data // received from a network request, for example
let json = try? JSONSerialization.jsonObject(with: data, options: [])

json顶层对象一般为字典或者反复组,我们得用as?+if进行判断转换

// Example JSON with object root:
/*
    {
        "someKey": 42.0,
        "anotherKey": {
            "someNestedKey": true
        }
    }
*/
if let dictionary = jsonWithObjectRoot as? [String: Any] {
    if let number = dictionary["someKey"] as? Double {
        // access individual value in dictionary
    }

    for (key, value) in dictionary {
        // access all key / value pairs in dictionary
    }

    if let nestedDictionary = dictionary["anotherKey"] as? [String: Any] {
        // access nested dictionary values by key
    }
}

// Example JSON with array root:
/*
    [
        "hello", 3, true
    ]
*/
if let array = jsonWithArrayRoot as? [Any] {
    if let firstObject = array.first {
        // access individual object in array
    }

    for object in array {
        // access all objects in array
    }

    for case let string as String in array {
        // access only string values in array
    }
}

Creating Model Objects from Values Extracted from JSON

若来只食堂的model

import Foundation

struct Restaurant {
    enum Meal: String {
        case breakfast, lunch, dinner
    }

    let name: String
    let location: (latitude: Double, longitude: Double)
    let meals: Set<Meal>
}

来自sever的JSON数据

{
    "name": "Caffè Macs",
    "coordinates": {
        "lat": 37.330576,
        "lng": -122.029739
    },
    "meals": ["breakfast", "lunch", "dinner"]
}

Writing an Optional JSON Initializer

extension Restaurant {
    init?(json: [String: Any]) {
        guard let name = json["name"] as? String,
            let coordinatesJSON = json["coordinates"] as? [String: Double],
            let latitude = coordinatesJSON["lat"],
            let longitude = coordinatesJSON["lng"],
            let mealsJSON = json["meals"] as? [String]
        else {
            return nil
        }

        var meals: Set<Meal> = []
        for string in mealsJSON {
            guard let meal = Meal(rawValue: string) else {
                return nil
            }

            meals.insert(meal)
        }

        self.name = name
        self.coordinates = (latitude, longitude)
        self.meals = meals
    }
}

Writing a JSON Initializer with Error Handling

enum SerializationError: Error {
    case missing(String)
    case invalid(String, Any)
}

extension Restaurant {
    init(json: [String: Any]) throws {
        // Extract name
        guard let name = json["name"] as? String else {
            throw SerializationError.missing("name")
        }

        // Extract and validate coordinates
        guard let coordinatesJSON = json["coordinates"] as? [String: Double],
            let latitude = coordinatesJSON["lat"],
            let longitude = coordinatesJSON["lng"]
        else {
            throw SerializationError.missing("coordinates")
        }

        let coordinates = (latitude, longitude)
        guard case (-90...90, -180...180) = coordinates else {
            throw SerializationError.invalid("coordinates", coordinates)
        }

        // Extract and validate meals
        guard let mealsJSON = json["meals"] as? [String] else {
            throw SerializationError.missing("meals")
        }

        var meals: Set<Meal> = []
        for string in mealsJSON {
            guard let meal = Meal(rawValue: string) else {
                throw SerializationError.invalid("meals", string)
            }

            meals.insert(meal)
        }

        // Initialize properties
        self.name = name
        self.coordinates = coordinates
        self.meals = meals
    }
}

Interactive Playgrounds

关于此可以去看本身之简文playground正确采取姿势

Literals in Playgrounds

Xcode7.1开始支持字面量,主要用来颜色、图片、文件

Strings in Swift 2

至于此可以错过押自己之简文汝确实懂swift
string吗?

Increasing Performance by Reducing Dynamic Dispatch

swift允许再次写超类的主意以及属性,这即需要以运转时接的访并且实施间接调用。这个技术叫做动态派发,这项技艺增加了语言表达的复杂和大度的runtime消耗以间接的运及。下面介绍三栽艺术消除动态派发:final、private、WholeModule
Optimization

告澳门新葡亰官网看下的代码

class ParticleModel {
    var point = ( 0.0, 0.0 )
    var velocity = 100.0

    func updatePoint(newPoint: (Double, Double), newVelocity: Double) {
        point = newPoint
        velocity = newVelocity
    }

    func update(newP: (Double, Double), newV: Double) {
        updatePoint(newP, newVelocity: newV)
    }
}

var p = ParticleModel()
for i in stride(from: 0.0, through: 360, by: 1.0) {
    p.update((i * sin(i), i), newV:i*1000)
}

便像面写的,编译器发出动态派发调用

  1. 调用p 的 update
  2. 调用p 的 updatePoint
  3. 取p 的 point长祖属性
  4. 获取p 的 速率

此间使用动态派发的因在ParticleModel的子类可能通过可计算属性重写point、velocity,也再度写update、updatePonit

动态派发调用的贯彻是透过搜寻method
table然后行间接调用。着相对于直接调用的速度必然是徐的。

Use final when you know that a declaration does not need to be overridden

final关键字会范围class、method、property不吃重写。能够安全之使编译器取消动态派发。point、velocity、updatePoint不进行动态派发,直接看,update进行动态派发

class ParticleModel {
    final var point = ( x: 0.0, y: 0.0 )
    final var velocity = 100.0

    final func updatePoint(newPoint: (Double, Double), newVelocity: Double) {
        point = newPoint
        velocity = newVelocity
    }

    func update(newP: (Double, Double), newV: Double) {
        updatePoint(newP, newVelocity: newV)
    }
}

final修饰类的时段,表明无克为子类化,因此指明函数、属性都是final

final class ParticleModel {
    var point = ( x: 0.0, y: 0.0 )
    var velocity = 100.0
    // ...
}

Infer final on declarations referenced in one file by applying the private keyword.

动用private关键字,限制以当下文件内,如果手上文件内没针对拖欠class的重写,那么编译器就会想其不适用动态派发

class ParticleModel {
    private var point = ( x: 0.0, y: 0.0 )
    private var velocity = 100.0

    private func updatePoint(newPoint: (Double, Double), newVelocity: Double) {
        point = newPoint
        velocity = newVelocity
    }

    func update(newP: (Double, Double), newV: Double) {
        updatePoint(newP, newVelocity: newV)
    }
}

及final一样,private也可修饰class

Use Whole Module Optimization to infer final on internal declarations.

internal默认的访问控制权限表明只有能够在模块可见。swift编译文件是模块独立的,无法确定internal声明在不同的文本是否让另行写了。但是如果全模块的优化是被之,所有的模块同时编译、能够允许编译器将internal推断其的可见性

public class ParticleModel {
    var point = ( x: 0.0, y: 0.0 )
    var velocity = 100.0

    func updatePoint(newPoint: (Double, Double), newVelocity: Double) {
        point = newPoint
        velocity = newVelocity
    }

    public func update(newP: (Double, Double), newV: Double) {
        updatePoint(newP, newVelocity: newV)
    }
}

var p = ParticleModel()
for i in stride(from: 0.0, through: times, by: 1.0) {
    p.update((i * sin(i), i), newV:i*1000)
}

Nullability and Objective-C

事实上对应的就是是只是选值

  • !表示非空
  • ?可空
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