从OC到Swift

作者: Stago | 来源:发表于2020-05-20 16:47 被阅读0次

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

func test() {
    // TODO: 未完成
}
func test2() {
    var age = 10
    // FIXME: u有待修复
    age += 20
}

public class Person {
    // MARK: - 属性
    var age = 0
    var weight = 0
    var height = 0
    
    // MARK: - 私有方法
    // MARK: 跑步
    private func run1() {}
    private func run2() {}
    // MARK: 走路
    private func walk1() {}
    private func walk2() {}
    
    // MARK: - 公共方法
    public func eat1() {}
    public func eat2() {}
}

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

// debug模式
#if DEBUG
// release模式
#else
#endif

#if TEST
print("test")
#endif

#if OTHER
print("other")
#endif

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
}

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
}

API可用性说明

@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 runn() {}
}

更多用法

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

import UIKit

class MYApplication : UIApplication {}

UIApplicationMain(CommandLine.argc,
                  CommandLine.unsafeArgv,
                  NSStringFromClass(MYApplication.self),
                  NSStringFromClass(AppDelegate.self))

从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 "Person.h"

Swift调用OC - Person.h

int sum(int a, int b);

@interface Person : 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;

Swift调用OC - Person.m

@implementation Person
- (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; }

Swift调用OC - Swift代码

var p = Person(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 Person.run() // Person +run
Person.eat("Pizza", other: "Banana") // Person +eat Pizza Banana print(sum(10, 20)) // 30

var p = Person(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 Person.run() // Person +run
Person.eat("Pizza", other: "Banana") // Person +eat Pizza Banana print(sum(10, 20)) // 30

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

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

OC调用Swift - Car.Swift

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") }
}

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

代表默认所有成员都会暴露给OC（包括扩展中定义的成员）
最终是否成功暴露，还需要考虑成员自身的访问级别

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

@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

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;
}

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(Car)
@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") }
}
extension Car {
    @objc(exec:v2:)
    func test() { print(price, band, "test") }
}
Car *c = [[Car alloc] initWithPrice:10.5 band:@"BMW"]; c.name = @"Bently";
c.price = 108.5;
[c drive]; // 108.5 Bently run
[c exec:10 v2:20]; // 108.5 Bently test [Car run]; // Car run

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

必须是被@objcMembers或@objc修饰的方法才可以定义选择器

@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))
    }
}

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: String = "1"
// 拼接
str.append("_2")
// 重载运算符 +
str = str + "_3"
// 重载运算符 +=
str += "_4"
// \()插值
str = "\(str)_5"
// 长度 9
print(str.count)

var str = "123456"
print(str.hasPrefix("123")) // true
print(str.hasSuffix("456")) // true

String 的插入和删除

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" }
var range = str.index(str.endIndex, offsetBy: -4)..<str.index(before: str.endIndex)
// hello_2_3_4
str.removeSubrange(range)

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

var str = "1_2_3_4_5"
// 1_2
var substr1 = str.prefix(3)
// 4_5
var substr2 = str.suffix(3)
// 1_2
var range = str.startIndex..<str.index(str.startIndex, offsetBy: 3)
var substr3 = str[range]

// 最初的String 1_2_3_4_5
print(substr3.base)

// Substring -> String
var str2 = String(substr3)

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

String 与 Character

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

var str = "jack"
// c是Character类型
var c = str[str.startIndex]

String相关的协议

BidirectionalCollection 协议包含的部分内容

startIndex、endIndex属性、index方法

String、Array都遵守了这个协议

RangeReplaceableCollection 协议包含的部分内容

append、insert、remove 方法

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

多行String

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

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

// 缩进以结尾的3引号为对齐线
let str = """
        1
            2
    3
        4
    """
    1
        2
3
    4

// 以下2个字符串是等价的
let str1 = "These are the same."
let str2 = """
These are the same.
"""

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

var str1: String = "jack"
var str2: NSString = "rose"

var str3 = str1 as NSString
var str4 = str2 as String

// ja
var 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）

Swift、OC桥接转换表

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

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

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

class Dog: NSObject {
    @objc dynamic func test1() {}
    func test2() {}
}

var d = Dog()
d.test1()
d.test2()

KVC\KVO

Swift 支持KVC\KVO的条件

属性所在的类、监听器最终继承自NSObject

用@objc dynamic 修饰对应的属性

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")
    }
}
var p = Person()
// observeValue Optional(20)
p.age = 20
// observeValue Optional(25)
p.setValue(25, forKey: "age")

block方式的KVO

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)
        }
    }
}
var p = Person()
// Optional(20)
p.age = 20
// Optional(25)
p.setValue(25, forKey: "age")

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

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 Person {}
extension Person {
    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 = Person()
print(p.age) // 0
p.age = 10
print(p.age) // 10

资源名管理

let img = UIImage(named: "logo")

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

performSegue(withIdentifier: "login_main", sender: self)

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

performSegue(withIdentifier: R.segue.login_main, sender: self)

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

这种作法实际上是参考了Android的资源名管理方式

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)
    }
}

资源名管理的其他思路

let img = UIImage(named: "logo")

let font = UIFont(name: "Arial", size: 14)

let img = R.image.logo

let font = R.font.arial(14)

enum R {
    enum image {
        static var logo = UIImage(named: "logo") }
    enum font {
        static func arial(_ size: CGFloat) -> UIFont? {
            UIFont(name: "Arial", size: size)
        }
    }
}

更多优秀的思路思考

https://github.com/mac-cain13/R.swift
https://github.com/SwiftGen/SwiftGen

多线程开发 - 异步

public typealias Task = () -> Void

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

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

private static 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)
    }
}

多线程开发 - 延迟

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

多线程开发 - 异步延迟

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

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

private static 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
}

多线程开发 - once

dispatch_once在Swift中已被废弃，取而代之

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
    }
}

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 static var lock = NSLock()
static func set(_ key: String, _ value: Any) {
    lock.lock()
    defer { lock.unlock() }
}

private static var lock = NSRecursiveLock()
static func set(_ key: String, _ value: Any) {
    lock.lock()
    defer { lock.unlock() }
}

从OC到Swift

MARK、TODO、FIXME

条件编译

打印

系统版本检测

API可用性说明

iOS程序的入口

Swift调用OC - Person.h

Swift调用OC - Person.m

Swift调用OC - Swift代码

Swift调用OC - @_silgen_name

OC调用Swift - Car.Swift

OC调用Swift - {targetName}-Swift.h

OC调用Swift - OC代码

OC调用Swift - @objc

选择器（Selector）

String

String 的插入和删除

Substring

String 与 Character

String相关的协议

多行String

String 与 NSString

Swift、OC桥接转换表

只能被class继承的协议

可选协议

dynamic

KVC\KVO

block方式的KVO

关联对象（Associated Object）

资源名管理

资源名管理的其他思路

多线程开发 - 异步

多线程开发 - 延迟

多线程开发 - 异步延迟

多线程开发 - once

多线程开发 - 加锁

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