swift中利用runtime交换方法的实现示例
作者：小峰书
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前言
Runtime介绍
学习一个东西至少要先知道它是个啥，你一定听说过“运行时是 Objective-C 的一个特色”，这里的“运行时”就是指 runtime 了。
老的方式initialize现在已经不适用了，需要用新的方式代替。
思路: 定义一个启动的协议，在app完成启动的方法里把需要做method swizzle的类跑一边协议的方法
第一种
1、Step One
protocol SelfAware: class {
static func awake()
}
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(capacity: typeCount)
}
}
2、step two
extension UIApplication {
private static let runOnce: Void = {
NothingToSeeHere.harmlessFunction()
}()
override open var next: UIResponder? {
// Called before applicationDidFinishLaunching
UIApplication.runOnce
return super.next
}
}
3、step three
遵循协议SelfAware,实现awake()
第二种(类似第一种)
1、创建一个swizzle注入的协议
public protocol SwizzlingInjection: class {
static func inject()
}
2、创建swizzle helper
open class SwizzlingManager {
//只会调用一次的方法
private static let doOnce: Any? = {
UIViewController.inject()
return nil
}()
open static func enableInjection() {
_ = SwizzlingManager.doOnce
}
}
3、给UIApplication 创建分类调用那个一次方法
extension UIApplication{
open override var next: UIResponder?{
SwizzlingManager.enableInjection()
return super.next
}
}
4、在你需要的类中遵循注入协议
extension UIViewController: SwizzlingInjection{
public static func inject() {
//确保不是子类
guard self === UIViewController.self else { return }
DispatchQueue.once(token: "com.moglo.urmoji.UIViewController") {
//do swizzle method
}
}
}
once只执行一次的方法
public extension DispatchQueue {
private static var _onceTracker = [String]()
public class func once(file: String = #file, function: String = #function, line: Int = #line, block:()->Void) {
let token = file + ":" + function + ":" + String(line)
once(token: token, block: block)
}
/**
Executes a block of code, associated with a unique token, only once. The code is thread safe and will
only execute the code once even in the presence of multithreaded calls.
- parameter token: A unique reverse DNS style name such as com.vectorform.<name> or a GUID
- parameter block: Block to execute once
*/
public class func once(token: String, block:()->Void) {
objc_sync_enter(self)
defer { objc_sync_exit(self) }
if _onceTracker.contains(token) {
return
}
_onceTracker.append(token)
block()
}
//delay
typealias Task = (_ cancel : Bool) -> Void
@discardableResult
static func delay(time : TimeInterval, task: @escaping () -> ()) -> Task? {
func dispatch_later(block : @escaping () -> ()) {
DispatchQueue.main.asyncAfter(deadline: DispatchTime.now() + time , execute: block)
}
var closure : (() -> ())? = task
var result : Task?
let delayedClosure : Task = {
cancel in
if let internalClosure = closure {
if cancel == false {
DispatchQueue.main.async(execute: internalClosure)
}
}
closure = nil
result = nil
}
result = delayedClosure
dispatch_later { () -> () in
if let delayedClosure = result {
delayedClosure(false)
}
}
return result
}
static func cancel(task : Task?) {
task?(true)
}
}
总结
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