3中的新特征

建议读1次swift
blog
来驾驭OC与swift差别以及swift版本变动细节

相较于Swift 2.2 , Swift 3做了极大的变动,逐步脱离OC的影子。
语法上很多目的去掉了NS初始,去掉了繁琐的命名。如 UIColor.redColor() 改为
UIColor.red , 变成了品质,还有方法的率先个参数倘若不内定
_调用的时候也要写参数名等等…

OC id -> Swift Any

优点,不需求手动装箱
使得OC API尤其灵活

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

急需注意的而是swift2不再提供隐式转换,因而NS桥接的供给您显示转换

本文主要商讨Swift 3中的一些坑和应用进程中的一些小技巧,排名无理由~~

Overriding methods and conforming to protocols

命名符合OC的科班,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 { ... }
}

AnyObject 、Any

从前一切项目基本只用 AnyObject
代表多数实例,基本也不和Any有何交集。因为Swift 2 针对Int、String
等结构体进行了转移,编写翻译器会活动桥接为NSNumber和NSString那种对象类型
,在swift3中AnyObject无法表示结构体了 。而 Any 能够表示 struct 、 class
、 func 等差不多拥有类型。

Untyped Collections

隐式桥接不设有了,需求运用as,swift3导入的cocoa接受了Any/AnyHashable,由此对于集合也足以选择[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)

fileprivate

在原有的swift中的private其实并不是真正的私有,假如1个变量定义为private,在同一个文件中的别的类依旧是足以访问到的。这几个场地在使用extension的时候很精通。

class User {
    private var name = "private"
}

extension User{
    var accessPrivate: String {
        return name
    }
}

那样带来了五个难题:

  • 当大家标记为private时,意为真的私有照旧文件内可共享呢?
  • 当我们假若打算为实在的个体时,必须确认保证这几个类照旧结构体在三个独立的文本里。不然恐怕同文件里别的的代码访问到。

透过,在swift 3中,新扩大了多少个
fileprivate来显式的申明,那一个成分的访问权限为文件内私有过去的private对应未来的fileprivate。现在的private则是真的的村办,离开了这些类照旧结构体的功能域外面就不可能访问

The AnyHashable Type

Any类型能够有所此外类型,可是Dictionary、Set要求Hasble,AnyHashble是swift3建议的hashable的超类,任何三个可hash的种类都落到实处了Anyhashble协议,比如String、Int

不再有CGRectMake,CGSizeMake等常用函数了

UIView(frame: CGRectMake(0, 0, 48, 48))
被改为
UIView(frame: CGRect(x: 0, y: 0, width: 48, height: 48))

// 'CGRectMake' is unavailable in Swift
// let frame = CGRect(0, 20, view.bounds.width, 130)        
// Swift 3.0 不再有CGRectMake,CGSizeMake等常用函数了        
 let frame = CGRect(x: 0, y: 20, width: view.bounds.width, height: 130)

Explicit Conversion for Unbridged Contexts

在一部分限量的场所swift不能够一贯桥接C和OC的筹划,比如id*,这么些时候api将会展现UnsafePointer<AnyObject>,此时须要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)
}

此外,OC的说道是类协议,不能够用结构体、枚举或别的轻量级的通用项目服从OC的磋商

参考文献

AnyObject Member Lookup

Any没有AnyObject的寻找行为艺术,由此无法动态的向Any发送新闻,可是AnyObject能够,此时内需更换

// 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能够拥有此外的结构体、枚举、元组也许别的的类别,OC的id在swift3等价于any,在swift第22中学须求手动封箱只怕转入类,swift3则不必要

// 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()))

急需留意的是swift3中对于常见的组织体类型将会桥接作为透明对象而不是cocoa对象,Int、UInt、Double、Bool会桥接为NSNumber,Int8,UInt16则仅仅桥接为透明对象。假若遭受了unrecognized selector sent to _SwiftValue标题,它象征OC尝试唤醒四个格局在swift
值类型上,此时大家须求手动管理

swift Any持有任一类型蕴涵Optional,就算OC api供给是nonull
id,Optional在未解包的状态下也得以当作参数字传送递,会招致runtime
error而不是编写翻译错误。swift3.0.1+Xoce8.1解决了上述难点,为了防止包容难题,不要借助于透明对象因为前景的swift可能会桥接到固定类型

Working with JSON in Swift

JSONSerialization Foundation framework

Extracting Values from JSON

JSONSerialization类方法jsonObject再次回到Any类型并且扔出万分倘若data无法分析

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许数组,大家得以行使as?+if举行判定转换

// 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

即便有个饭店的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

有关那里能够去看本人的简文playground正确行使姿势

Literals in Playgrounds

Xcode7.1开端帮助字面量,首要用于颜色、图片、文件

Strings in Swift 2

关于那里能够去看自身的简文您确实懂swift
string吗?

Increasing Performance by Reducing Dynamic Dispatch

swift允许重写超类的法门和天性,这就供给在运作时刻接的拜会并且实施间接调用。这些技术叫做动态派发,那项技术扩充了语言表明的繁杂和多量的runtime消耗在直接的行使上。上边介绍三种方式消除动态派发:final、private、WholeModule
Optimization

请看上边包车型大巴代码

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)
}

就像下面写的,编写翻译器发出动态派发调用

  1. 调用p 的 update
  2. 调用p 的 updatePoint
  3. 取得p 的 point元祖属性
  4. 获取p 的 速率

此间使用动态派发的缘故在于ParticleModel的子类恐怕通过可计算属性重写point、velocity,也重写update、updatePonit

动态派发调用的兑现是透过搜寻method
table然后执行直接调用。着绝对于直接调用的进程自然是慢的。

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

final关键字可以范围class、method、property不被重写。能够安全的驱动编写翻译器裁撤动态派发。point、velocity、updatePoint不进行动态派发,直接待上访问,update实行动态派发

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修饰类的时候,申明无法被子类化,因而指明函数、属性都以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.

利用private关键字,限制在当下文件内,假若当前文件内尚未对该class的重写,那么编写翻译器就会推断它不适用动态派发

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)
    }
}

与final一样,private也足以修饰class

Use Whole Module Optimization to infer final on internal declarations.

internal暗中同意的访问控制权限评释仅能够在模块可知。swift编写翻译文件是模块独立的,不可能明确internal注明在分化的公文是不是被重写了。可是要是一切模块的优化是敞开的,全部的模块同时编写翻译、能够允许编写翻译器将internal揣测它的可知性

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

实则对应的便是可选值

  • !表示非空
  • ?可空