23-Swift从OC到Swift

1.MARK、TODO、FIXME

- MARK: 类似于OC中的 #pragma mark
- MARK: - 类似于OC中的 #pragma mark -
- TODO: 用于标记未完成的任务
- FIXME: 用于标记待修复的问题

2.条件编译

 // 操作系统:macOS\iOS\tvOS\watchOS\Linux\Android\Windows\FreeBSD #if os(macOS) || os(iOS)
// CPU架构:i386\x86_64\arm\arm64
#elseif arch(x86_64) || arch(arm64)
// swift版本
#elseif swift(<5) && swift(>=3)
// 模拟器
#elseif targetEnvironment(simulator) // 可以导入某模块
#elseif canImport(Foundation)
#else
#endif

3.打印

func log<T>(_ msg: T,
           file: NSString = #file,
           line: Int = #line,
           fn: String = #function) {
   #if DEBUG
   let prefix = "\(file.lastPathComponent)_\(line)_\(fn):"
   print(prefix, msg)
   #endif
}

4.系统版本检测

if #available(iOS 10, macOS 10.12, *) {
//    对于iOS平台，只在iOS10及以上版本执行
//    对于macOS平台，只在macOS 10.12及以上版本执行 // 最后的*表示在其他所有平台都执行
}

5.API可用性说明

do {
   @available(iOS 10, macOS 10.15, *)
   class Person {}
   struct Student {
       @available(*, unavailable, renamed: "study")
       func study_() {}
       func study() {}
       
       @available(iOS, deprecated: 11)
       @available(macOS, deprecated: 10.12)
       func run() {}
   }
}
/// 更多用法参考:https://docs.swift.org/swift-book/ReferenceManual/Attributes.html

6.iOS程序的入口

• 在AppDelegate上面默认有个@UIApplicationMain标记，这表示
• 编译器自动生成入口代码(main函数代码)，自动设置AppDelegate为APP的代理
• 也可以删掉@UIApplicationMain，自定义入口代码:新建一个main.swift文件

7.Swift调用OC

• 新建1个桥接头文件，文件名格式默认为:{targetName}-Bridging-Header.h
• 在{targetName}-Bridging-Header.h 文件中 #import OC需要暴露给Swift的内容
  • import "MJPerson.h"

//MARK: OC代码：
MJPerson.h
int sum(int a, int b);
@interface MJPerson : NSObject
@property (nonatomic, assign) NSInteger age;
@property (nonatomic, copy) NSString *name;
- (instancetype)initWithAge:(NSInteger)age name:(NSString *)name;
+ (instancetype)personWithAge:(NSInteger)age name:(NSString *)name;
- (void)run;
+ (void)run;
- (void)eat:(NSString *)food other:(NSString *)other;
+ (void)eat:(NSString *)food other:(NSString *)other;
@end

MJPerson.m
@implementation MJPerson
- (instancetype)initWithAge:(NSInteger)age name:(NSString *)name {
 if (self = [super init]) {
     self.age = age;
     self.name = name;
 }
   return self;
}
+ (instancetype)personWithAge:(NSInteger)age name:(NSString *)name {
 return [[self alloc] initWithAge:age name:name];
}
+ (void)run { NSLog(@"Person +run"); }
- (void)run { NSLog(@"%zd %@ -run", _age, _name); }
+ (void)eat:(NSString *)food other:(NSString *)other {
     NSLog(@"Person +eat %@ %@", food, other);
 }
- (void)eat:(NSString *)food other:(NSString *)other {
   NSLog(@"%zd %@ -eat %@ %@", _age, _name, food, other);
   }
@end
int sum(int a, int b) { return a + b; }

8.Swift调用OC – Swift代码

var p = MJPerson(age: 10, name: "Jack")
p.age = 18
p.name = "Rose"
p.run()
// 18 Rose -run
p.eat("Apple", other: "Water")
// 18 Rose -eat Apple Water
MJPerson.run()
// Person +run
MJPerson.eat("Pizza", other: "Banana")
// Person +eat Pizza Banana
print(sum(10, 20))
// 30

9.Swift调用OC – @_silgen_name

• 如果C语言暴露给Swift的函数名跟Swift中的其他函数名冲突了
• 可以在Swift中使用 @_silgen_name 修改C函数名

//C语言
int sum(int a, int b) {
 return a + b;
}

// Swift
@_silgen_name("sum")
func swift_sum(_ v1: Int32, _ v2: Int32) -> Int32
print(swift_sum(10, 20)) // 30
print(sum(10, 20)) // 30

10.OC调用Swift

• Xcode已经默认生成一个用于OC调用Swift的头文件，文件名格式是: {targetName}-Swift.h

11.OC调用Swift – Car.swift

• Swift暴露给OC的类最终继承自NSObject
• 使用@objc修饰需要暴露给OC的成员
• 使用 @objcMembers修饰类
  1.代表默认所有成员都会暴露给OC(包括扩展中定义的成员)
  2.最终是否成功暴露，还需要考虑成员自身的访问级别

import Foundation
@objcMembers class Car: NSObject {
   var price: Double
   var band: String
   init(price: Double, band: String) {
       self.price = price
       self.band = band
   }
   func run() { print(price, band, "run") }
   static func run() { print("Car run") }
}

extension Car {
   func test() { print(price, band, "test") }
}

12.OC调用Swift – {targetName}-Swift.h

• Xcode会根据Swift代码生成对应的OC声明，写入{targetName}-Swift.h 文件

// MARK: OC代码：
@interface Car : NSObject
@property (nonatomic) double price;
@property (nonatomic, copy) NSString * _Nonnull band;
- (nonnull instancetype)initWithPrice:(double)price band:(NSString * _Nonnull)band OBJC_DESIGNATED_INITIALIZER; - (void)run;
+ (void)run;
- (nonnull instancetype)init SWIFT_UNAVAILABLE;
+ (nonnull instancetype)new SWIFT_UNAVAILABLE_MSG("-init is unavailable");
@end
@interface Car (SWIFT_EXTENSION(备课_Swift)) - (void)test;
@end

13.OC调用Swift – OC代码

int sum(int a, int b) {
 Car *c = [[Car alloc] initWithPrice:10.5 band:@"BMW"];
 c.band = @"Bently";
 c.price = 108.5;
 [c run]; // 108.5 Bently run
 [c test]; // 108.5 Bently test [Car run]; // Car run
 return a + b;
}

14.OC调用Swift – @objc

• 可以通过@objc 重命名Swift暴露给OC的符号名(类名、属性名、函数名等)

@objc(MJCar)
@objcMembers class Car: NSObject {
   var price: Double
   @objc(name)
   var band: String
   init(price: Double, band: String) {
       self.price = price
       self.band = band
   }

   @objc(drive)
   func run() { print(price, band, "run")}
   static func run() { print("Car run") }
}

MJCar *c = [[MJCar alloc] initWithPrice:10.5 band:@"BMW"];
c.name = @"Bently";
c.price = 108.5;
[c drive]; // 108.5 Bently run

15.选择器(Selector)

• Swift中依然可以使用选择器，使用#selector(name)定义一个选择器 必须是@objcMembers或@objc修饰的方法才可以定义选择器

do {
   @objcMembers class Person: NSObject {
       func test1(v1: Int) {
           print("test1")
       }
       func test2(v1: Int, v2: Int) {
           print("test2(v1:v2:)")
       }
       func test2(_ v1: Double, _ v2: Double) {
           print("test2(_:_:)")
       }
       func run() {
           perform(#selector(test1))
           perform(#selector(test1(v1:)))
           perform(#selector(test2(v1:v2:)))
           perform(#selector(test2(_:_:)))
           perform(#selector(test2 as (Double, Double) -> Void))
       }
   }
}

16.String

• Swift的字符串类型String，跟OC的NSString，在API设计上还是有较大差异

// 空字符串
var emptyStr1 = ""
var emptyStr2 = String()
var str = "123456"
print(str.hasPrefix("123")) // true
var str1: String = "1" // 拼接，jack_rose str.append("_2")
// 重载运算符 +
str1 = str1 + "_3" // 重载运算符 += str += "_4"
// \()插值
str1 = "\(str1)_5"
// 长度，9，1_2_3_4_5 print(str.count)

17.String的插入和删除

do {
   var str = "1_2"
   // 1_2_
   str.insert("_", at: str.endIndex)
   // 1_2_3_4
   str.insert(contentsOf: "3_4", at: str.endIndex)
   // 1666_2_3_4
   str.insert(contentsOf: "666", at: str.index(after: str.startIndex))
   // 1666_2_3_8884
   str.insert(contentsOf: "888", at: str.index(before: str.endIndex))
   // 1666hello_2_3_8884
   str.insert(contentsOf: "hello", at: str.index(str.startIndex, offsetBy: 4))
    // 666hello_2_3_8884
   str.remove(at: str.firstIndex(of: "1")!)
   // hello_2_3_8884
   str.removeAll { $0 == "6" }
   let range = str.index(str.endIndex, offsetBy: -4)..<str.index(before: str.endIndex)
   // hello_2_3_4
   str.removeSubrange(range)
}

18.Substring

• String可以通过下标、 prefix、 suffix等截取子串，子串类型不是String，而是Substring

do {
    let str = "1_2_3_4_5"
    // 1_2
    let substr1 = str.prefix(3)
    print(substr1)
    // 4_5
    let substr2 = str.suffix(3)
    print(substr2)
    // 1_2
    let range = str.startIndex..<str.index(str.startIndex, offsetBy: 3)
    let substr3 = str[range]
    // 最初的String，1_2_3_4_5 print(substr3.base)
    // Substring -> String
    let str2 = String(substr3)
    print(str2)
    //Substring和它的base，共享字符串数据
    //Substring发生修改 或者 转为String时，会分配新的内存存储字符串数据
}

19.String 与 Character

for c in "jack" { // c是Character类型 print(c)
    print(c)
}

do {
    let str = "jack"
    // c是Character类型
    let c = str[str.startIndex]
    print(str, c)
}

20.String相关的协议

• BidirectionalCollection 协议包含的部分内容
  1.startIndex 、 endIndex 属性、index 方法
  2.String、Array 都遵守了这个协议
• RangeReplaceableCollection 协议包含的部分内容
  1.append、insert、remove 方法
  2.String、Array 都遵守了这个协议
• Dictionary、Set 也有实现上述协议中声明的一些方法，只是并没有遵守上述协议

21.多行String

do {
    let str = """
1
    "2"
3
    '4'
"""
    print(str)
}

// 如果要显示3引号，至少转义1个引号
do {
    let str = """
Escaping the first quote \"""
Escaping two quotes \"\""
Escaping all three quotes \"\"\"
"""
    print(str)
}

// 缩进以结尾的3引号为对齐线
do {
    let str = """
        1
            2
    3
        4
    """
    print(str)
}

// 以下2个字符串是等价的
do {
    let str1 = "These are the same."
    let str2 = """
    These are the same.
    """
    if str1 == str2 {
        print("equal")
    }else{
        print("no equal")
    }
}

22.String 与 NSString

• String 与 NSString 之间可以随时随地桥接转换
  • 如果你觉得String的API过于复杂难用，可以考虑将String转为NSString

do {
    let str1: String = "jack"
    let str2: NSString = "rose"
    
    let str3 = str1 as NSString
    let str4 = str2 as String
    print(str4)
    
    // ja
    let str5 = str3.substring(with: NSRange(location: 0, length: 2))
    print(str5)
}
//比较字符串内容是否等价
//String使用 == 运算符
//NSString使用isEqual方法，也可以使用 == 运算符(本质还是调用了isEqual方法)

23.Swift、OC桥接转换表

image.png

24.只能被class继承的协议

protocol Runnable1: AnyObject {}
protocol Runnable2: class {}
@objc protocol Runnable3 {}
//被@objc 修饰的协议，还可以暴露给OC去遵守实现

25.可选协议

// 可以通过@objc 定义可选协议，这种协议只能被class 遵守
@objc protocol Runnable {
    func run1()
    @objc optional func run2()
    func run3()
}
class Dog: Runnable {
    func run3() { print("Dog run3") }
    func run1() { print("Dog run1") }
}
var d = Dog()
d.run1() // Dog run1 d.run3() // Dog run3

26.dynamic

• 被 @objc dynamic 修饰的内容会具有动态性，比如调用方法会走runtime那一套流程

do {
    class Dog: NSObject {
        @objc dynamic func test1() {}
        func test2() {}
    }
    let d = Dog()
    d.test1()
    d.test2()
}

27.KVC\KVO

• Swift 支持 KVC \ KVO 的条件
  1.属性所在的类、监听器最终继承自 NSObject
  2.用 @objc dynamic 修饰对应的属性

do {
    class Observer: NSObject {
        override func observeValue(forKeyPath keyPath: String?,
                                   of object: Any?,
                                   change: [NSKeyValueChangeKey : Any]?,
                                   context: UnsafeMutableRawPointer?) {
            print("observeValue", change?[.newKey] as Any)
        }
    }
    
    class Person: NSObject {
        @objc dynamic var age: Int = 0
        var observer: Observer = Observer()
        override init() {
            super.init()
            self.addObserver(observer, forKeyPath: "age", options: .new, context: nil)
        }
        deinit {
            self.removeObserver(observer, forKeyPath: "age")
        }
    }
    
    let p = Person()
    // observeValue Optional(20)
    p.age = 20
    // observeValue Optional(25)
    p.setValue(25, forKey: "age")
}

28.block方式的KVO

do {
    class Person: NSObject {
        @objc dynamic var age: Int = 0
        var observation: NSKeyValueObservation?
        override init() {
            super.init()
            observation = observe(\Person.age, options: .new) {
                    (person, change) in
                print(change.newValue as Any) }
        }
    }
    let p = Person()
    // Optional(20)
    p.age = 20
    // Optional(25)
    p.setValue(25, forKey: "age")
}

29.关联对象(Associated Object)

• 在Swift中，class依然可以使用关联对象
• 默认情况，extension不可以增加存储属性 p借助关联对象，可以实现类似extension为class增加存储属性的效果

class Person1 {}
extension Person1 {
    private static var AGE_KEY: Void?
    var age: Int {
        get {
            (objc_getAssociatedObject(self, &Self.AGE_KEY) as? Int) ?? 0
        }
        set {
            objc_setAssociatedObject(self, &Self.AGE_KEY, newValue, .OBJC_ASSOCIATION_ASSIGN)
        }
    }
}
var p = Person1()
print(p.age) // 0
p.age = 10
print(p.age) // 10

30.资源名管理

let img = UIImage(named: "logo")

let btn = UIButton(type: .custom)
btn.setTitle("添加", for: .normal)

enum R {
    enum string: String {
        case add = "添加"
    }
    enum image: String {
        case logo
    }
    enum segue: String {
        case login_main
    }
}

extension UIImage {
    convenience init?(_ name: R.image) {
        self.init(named: name.rawValue) }
}
extension UIViewController {
    func performSegue(withIdentifier identifier: R.segue, sender: Any?) {
        performSegue(withIdentifier: identifier.rawValue, sender: sender) }
}
extension UIButton {
    func setTitle(_ title: R.string, for state: UIControl.State) {
        setTitle(title.rawValue, for: state)
    }
}


let img1 = UIImage(R.image.logo)
let btn1 = UIButton(type: .custom)
btn1.setTitle(R.string.add, for: .normal)

//这种做法实际上是参考了Android的资源名管理方式

31.资源名管理的其他思路

let img2 = UIImage(named: "logo")
let font2 = UIFont(name: "Arial", size: 14)
//更多优秀的思路参考 https://github.com/mac-cain13/R.swift https://github.com/SwiftGen/SwiftGen

enum R1 {
    enum image {
        static var logo = UIImage(named: "logo") }
    enum font {
        static func arial(_ size: CGFloat) -> UIFont? {
            UIFont(name: "Arial", size: size)
        }
    }
}
let img3 = R1.image.logo
let font3 = R1.font.arial(14)

32.多线程开发 – 异步

public typealias Task = () -> Void
private func _async(_ task: @escaping Task,
                   _ mainTask: Task? = nil) {

    let item = DispatchWorkItem(block: task)
    DispatchQueue.global().async(execute: item)
    if let main = mainTask {
        item.notify(queue: DispatchQueue.main, execute: main)
    }

}
public func async(_ task: @escaping Task) {
    _async(task)
}

public func async(_ task: @escaping Task, _ mainTask: @escaping Task) {
    _async(task, mainTask)
}

33.多线程开发 – 延迟

@discardableResult
public func delay(_ seconds: Double,
                         _ block: @escaping Task) -> DispatchWorkItem {
    let item = DispatchWorkItem(block: block)
    DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + seconds, execute: item)
    return item
}

34.多线程开发 – 异步延迟

@discardableResult
public func asyncDelay(_ seconds: Double,
                              _ task: @escaping Task) -> DispatchWorkItem {
    return _asyncDelay(seconds, task)
}

@discardableResult
public func asyncDelay(_ seconds: Double,
                              _ task: @escaping Task,
                              _ mainTask: @escaping Task) -> DispatchWorkItem {
    return _asyncDelay(seconds, task, mainTask)
}

private func _asyncDelay(_ seconds: Double,
                                _ task: @escaping Task,
                                _ mainTask: Task? = nil) -> DispatchWorkItem {
    let item = DispatchWorkItem(block: task)
    DispatchQueue.global().asyncAfter(deadline: DispatchTime.now() + seconds, execute: item)
    if let main = mainTask {
        item.notify(queue: DispatchQueue.main, execute: main)
    }
    return item
}

35.多线程开发 – once

• dispatch_once在Swift中已被废弃，取而代之 p可以用类型属性或者全局变量\常量
• 默认自带 lazy + dispatch_once 效果

fileprivate let initTask2: Void = {
    print("initTask2---------")
}()
class ViewController: UIViewController {
    static let initTask1: Void = {
        print("initTask1---------")
    }()
    override func viewDidLoad() {
        super.viewDidLoad()
        let _ = Self.initTask1
        let _ = initTask2
    }
}

36.多线程开发 – 加锁

-gcd信号量
class Cache {
    private static var data = [String: Any]()
    private static var lock = DispatchSemaphore(value: 1)
    static func set(_ key: String, _ value: Any) {
        lock.wait()
        defer {
            lock.signal()
        }
        data[key] = value
    }
}

- Foundation
private var lock = NSLock()
private var data = [String: Any]()
func set(_ key: String, _ value: Any) {
    lock.lock()
    defer {
        lock.unlock()
    }
    data[key] = value
}

private var lock1 = NSRecursiveLock()
func set1(_ key: String, _ value: Any) {
    lock1.lock()
    defer {
        lock1.unlock()
    }
    data[key] = value
}