1.我们知道Objective-C是一门动态性语言，能够通过runtime API调用和替换任意方法，那Swift也具有这些动态性吗？
- 分析示例
PureSwiftClass是纯Swift类，MuixSwiftClass是一个继承自NSObject的类。两个类中都包含了属性、方法。
//MARK: - 纯SwiftClass
class PureSwiftClass {
@objc var bolValue: Bool = false
@objc var age: Int = 0
@objc var height: Float = 0
@objc var name: String?
@objc var exName: String?
@objc func testPureAction() {
print("PureSwiftClass.testPureAction")
}
}
class MuixSwiftClass: UIViewController {
@objc var bolValue: Bool = false
@objc var age: Int = 0
@objc var height: Float = 0
@objc var name: String?
@objc var exName: String?
override func viewDidLoad() {
super.viewDidLoad()
}
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
}
@objc func createSubView(view : UIView) {
print("MuixSwiftClass.createSubView")
}
@objc func testVoidWithBool(boolValue : Bool , tempInt : Int , tempFloat : Float , str : String , obj : AnyObject) {
print("MuixSwiftClass.testVoidWithBool")
}
// @objc func testVoidWithTuple(boolValue : Bool , tempInt : Int , tempFloat : Float) -> (Bool , Int , Float){
// print("MuixSwiftClass.testVoidWithTuple")
// return (boolValue,tempInt,tempFloat)
// }
//
// @objc func testVoidWithCharacter(char : Character ) {
// print("MuixSwiftClass.testVoidWithCharacter")
// }
}
- 动态获取方法、属性的方法
func showClsRuntime (cls: AnyClass) {
print("----------方法列表开始-----------")
var methodNum: UInt32 = 0
let methodList: UnsafeMutablePointer<objc_property_t>! = class_copyMethodList(cls, &methodNum)
for index in 0..<numericCast(methodNum) {
let method: Method = methodList[index]
if let methodName: String = String(utf8String: property_getName(method)){
print(methodName)
}
}
print("----------方法列表结束-----------")
free(methodList)
print("----------属性列表开始-----------")
var propertyNum: UInt32 = 0
let propertyList: UnsafeMutablePointer<objc_property_t>! = class_copyPropertyList(cls, &propertyNum)
for index in 0..<numericCast(propertyNum) {
let property: objc_property_t = propertyList[index]
if let proName: String = String(utf8String: property_getName(property)){
print(proName)
}
}
free(propertyList)
print("----------属性列表开始-----------")
}
- 方法调用示例
showClsRuntime(cls: MuixSwiftClass.self)
showClsRuntime(cls: PureSwiftClass.self)
- 打印结果
MuixSwiftClass动态获取方法、属性
----------方法列表开始-----------
bolValue
setBolValue:
exName
setExName:
createSubViewWithView:
testVoidWithBoolWithBoolValue:tempInt:tempFloat:str:obj:
.cxx_destruct
name
setName:
initWithCoder:
initWithNibName:bundle:
viewDidLoad
viewDidAppear:
height
setHeight:
setAge:
age
----------方法列表结束-----------
----------属性列表开始-----------
bolValue
age
height
name
exName
----------属性列表结束-----------
PureSwiftClass动态获取方法、属性
----------方法列表开始-----------
bolValue
setBolValue:
exName
setExName:
testPureActionWithAId:
name
setName:
height
setHeight:
setAge:
age
----------方法列表结束-----------
----------属性列表开始-----------
bolValue
age
height
name
exName
----------属性列表结束-----------
纯Swfit类PureSwiftClass都未获取到方法、属性，对于MuixSwiftClass获取成功。
1.纯Swift类的函数调用已经不再是Objective-c的运行时发消息，而是类似C++的vtable，在编译时就确定了调用哪个函数，所以没法通过runtime获取方法、属性。
2.MuixSwiftClass继承自UIViewController，基类NSObject，而Swift为了兼容Objective-C，凡是继承自NSObject的类都会保留其动态性，所以我们能通过runtime拿到他的方法。这里有一点说明:老版本的Swift（如2.2）是编译期隐式的自动帮你加上了@objc，而4.0以后版本的Swift编译期去掉了隐式特性，必须使用显式标示！
3.可以看到MuixSwiftClass中有两个注释掉的方法。因为此两个方法在加上@objc后，Xcode直接报错提示此方法参数类型不能映射到OC类型，runtime也就无法获取。
4.因为方法参数里的Character和Tuple两个类型是Swift独有的，无法映射到OC的类型。
5.结合以上几点，不管是纯Swift类还是继承自NSObject的类只要在属性和方法前面添加@objc关键字就可以使用runtime。
Method Swizzling
MuixSwiftClass方法替换代码
extension MuixSwiftClass {
@objc func swizzle_viewWillAppear(_ animated: Bool) {
swizzle_viewWillAppear(animated)
print("swizzle_viewWillAppear")
}
}
extension MuixSwiftClass: SelfAware{
static func awake() {
takeOnceTime
}
private static let takeOnceTime: Void = {
let originalSelector = #selector(viewWillAppear(_:))
let swizzledSelector = #selector(swizzle_viewWillAppear(_:))
swizzlingForClass(MuixSwiftClass.self, originalSelector: originalSelector, swizzledSelector: swizzledSelector)
}()
}
PureSwiftClass方法替换代码
extension PureSwiftClass {
@objc func swizzle_testPureAction() {
swizzle_testPureAction()
print("swizzle_testPureAction")
}
}
extension PureSwiftClass: SelfAware {
static func awake() {
self.takeOnceTime
}
private static let takeOnceTime: Void = {
let originalSelector = #selector(testPureAction)
let swizzledSelector = #selector(swizzle_testPureAction)
swizzlingForClass(OtherPureSwiftClass.self, originalSelector: originalSelector, swizzledSelector: swizzledSelector)
}()
}
方法调用代码（具体调用原理可参考 资源链接）
protocol SelfAware: class {
static func awake()
static func swizzlingForClass(_ forClass: AnyClass, originalSelector: Selector, swizzledSelector: Selector)
}
extension SelfAware {
static func swizzlingForClass(_ forClass: AnyClass, originalSelector: Selector, swizzledSelector: Selector) {
let originalMethod = class_getInstanceMethod(forClass, originalSelector)
let swizzledMethod = class_getInstanceMethod(forClass, swizzledSelector)
guard (originalMethod != nil && swizzledMethod != nil) else {
return
}
if class_addMethod(forClass, originalSelector, method_getImplementation(swizzledMethod!), method_getTypeEncoding(swizzledMethod!)) {
class_replaceMethod(forClass, swizzledSelector, method_getImplementation(originalMethod!), method_getTypeEncoding(originalMethod!))
} else {
method_exchangeImplementations(originalMethod!, swizzledMethod!)
}
}
}
class NothingToSeeHere {
static func harmlessFunction() {
let typeCount = Int(objc_getClassList(nil, 0))
let types = UnsafeMutablePointer<AnyClass>.allocate(capacity: typeCount)
let autoreleasingTypes = AutoreleasingUnsafeMutablePointer<AnyClass>(types)
objc_getClassList(autoreleasingTypes, Int32(typeCount))
for index in 0 ..< typeCount {
(types[index] as? SelfAware.Type)?.awake()
}
types.deallocate()
}
}
extension UIApplication {
private static let runOnce: Void = {
NothingToSeeHere.harmlessFunction()
}()
override open var next: UIResponder? {
UIApplication.runOnce
return super.next
}
}
打印如下
swizzle_viewWillAppear
PureSwiftClass.testPureAction
