swift5.1学习-13.从OC到Swift

1.注释标记MARK、TODO、FIXME

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

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

#endif

3.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
}

4.iOS程序的入口

5.Swift调用OC

在Swift中使用 @_silgen_name 修改C函数名，避免函数名冲突

// 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

6.OC调用Swift

@objcMembers class Car: NSObject {
//方法属性等 
}

@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") }
}
extension Car {
    @objc(exec:v2:)
func test() { print(price, band, "test") } }

//调用
MJCar *c = [[MJCar 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 [MJCar run]; // Car run

@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))
} }

7.KVC\KVO

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")
 class Observer: NSObject {
override func observeValue(forKeyPath keyPath: String?,
                               of object: Any?,
                               change: [NSKeyValueChangeKey : Any]?,
                               context: UnsafeMutableRawPointer?) {
print("observeValue", change?[.newKey] as Any) }
}

8.关联对象(Associated Object)

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

9.多线程加锁

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