AOP全称叫Aspect-Oriented Programming，中文名叫面向切面编程，在iOS平台中，AOP一般使用Runtime实现
本文demo
在UIKit提供的用户交互接口里，主要可以分为两种：
Delegate类UITableView、UICollectionView的点击事件，特点是方法名定死，使用weak属性持有响应对象Target-Action类UIControl、UIGestureRecognizer的回调事件，特点是方法名可自定义，方法参数可有可无，使用weak属性持有响应对象，支持多个响应者
通常会拦截setDelegate:的方法，此时拦截到的delegate对象即为响应对象，再通过判断该响应对象是否实现了相应的代理方法，构建相同的方法进行交换，网上百度到的大部分都是这种实现的逻辑
但此方案存在如下问题：
- 如果父类实现了
setDelegate:和相应的代理方法，而具体的业务逻辑是由子类override重写的代理方法，那么判断到的埋点数据有可能存在问题 - 如果同一个页面有多个
UITableView，那么setDelegate:方法也会实现多次，此时需要防止出现多重交换的情况
参考文章中给出了其他方案：
- 拦截
setDelegate:方法，重新创建一个proxy类绑定代理并实现相应的代理方法，并将该proxy类的对象交换给系统的delegate - 使用
Runtime将自定义的proxy类的对象添加到控件中持有 - 当触发代理方法时，系统实际持有
delegate属性是proxy类的对应，会将触发方法发送到proxy类中，此时就可以进一步判断是否需要将代理方法继续转发到业务层
import UIKit
/// 使用此类替代系统的delegate
class GHUITableViewDelegateProxy: NSObject, UITableViewDelegate {
weak var delegate: UITableViewDelegate?
override func responds(to aSelector: Selector!) -> Bool {
var hasSelector: Bool = false
if self.delegate == nil {
return hasSelector
}
hasSelector = self.delegate?.responds(to: aSelector) ?? true
return hasSelector
}
override func forwardingTarget(for aSelector: Selector!) -> Any? {
if self.delegate == nil {
return super.forwardingTarget(for: aSelector)
}
if self.delegate?.responds(to: aSelector) == false {
return super.forwardingTarget(for: aSelector)
}
return self.delegate
}
// MARK: UITableViewDelegate
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
if self.delegate == nil {
return
}
if (self.delegate?.responds(to: #selector(tableView(_:didSelectRowAt:)))) == false {
return
}
UITableViewTrack.shared.trackTableView(tableView, didSelectRowAt: indexPath)
self.delegate?.tableView?(tableView, didSelectRowAt: indexPath)
}
}
private func swizzle(_ tableView: UITableView.Type) {
let selectors: Array<Array<Selector>> = [
[
#selector(setter: tableView.delegate),
#selector(tableView.gh_setDelegate(_:))
],
]
for item in selectors {
let originalSelector: Selector = item[0]
let swizzledSelector: Selector = item[1]
let originalMethod: Method? = class_getInstanceMethod(tableView, originalSelector)
let swizzledMethod: Method? = class_getInstanceMethod(tableView, swizzledSelector)
if originalMethod == nil {
continue
}
let didAddMethod: Bool = class_addMethod(tableView, originalSelector, method_getImplementation(swizzledMethod!), method_getTypeEncoding(swizzledMethod!))
if didAddMethod {
class_replaceMethod(tableView, swizzledSelector, method_getImplementation(originalMethod!), method_getTypeEncoding(originalMethod!))
} else {
method_exchangeImplementations(originalMethod!, swizzledMethod!)
}
}
}
var ghUITableViewDelegateProxyKey = "GHUITableViewDelegateProxyKey"
extension UITableView {
var ghUITableViewDelegateProxy: GHUITableViewDelegateProxy? {
set {
objc_setAssociatedObject(self, &ghUITableViewDelegateProxyKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
}
get {
return objc_getAssociatedObject(self, &ghUITableViewDelegateProxyKey) as? GHUITableViewDelegateProxy
}
}
private static let dispatchOnceTime: Void = {
swizzle(UITableView.self)
}()
@objc open class func startAOP() {
guard self === UITableView.self else { return }
UITableView.dispatchOnceTime
}
// MARK: 交换的方法
// 交换setdelegate的方法
@objc func gh_setDelegate(_ delegate: UITableViewDelegate?) {
// 使用GHUITableViewDelegateProxy替代原来系统的UITableViewDelegate
self.ghUITableViewDelegateProxy = GHUITableViewDelegateProxy()
self.ghUITableViewDelegateProxy?.delegate = delegate
self.gh_setDelegate(self.ghUITableViewDelegateProxy)
}
}
按照参考文章中上图的逻辑设计代码如下：
import UIKit
/// 自定义一个action类，由此类的实例对象替代外部传入的action
class GHUITapGestureRecognizerAction: NSObject {
// 弱应用，防止循环应用
weak var target: UIResponder?
var action: Selector?
@objc func ghGestureRecognizerAction(sender: UIGestureRecognizer?) -> Void {
if self.target == nil {
return
}
if self.action == nil {
return
}
UITapGestureRecognizerTrack.shared.trackGRAction(sender as? UITapGestureRecognizer, action: self.action!, target: self.target)
if ((target?.responds(to: action)) == true) {
target?.perform(action, with: sender)
}
}
}
var ghGestureActionsKey: String = "GHGestureActionsKey"
extension UIResponder {
/// 使用runtime给UIResponder扩展一个属性
var ghGestureActions: Array<GHUITapGestureRecognizerAction>? {
set {
objc_setAssociatedObject(self, &ghGestureActionsKey, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
}
get {
return objc_getAssociatedObject(self, &ghGestureActionsKey) as? Array<GHUITapGestureRecognizerAction>
}
}
}
private func swizzle(_ gesture: UITapGestureRecognizer.Type) {
let selectors: Array<Array<Selector>> = [
[
#selector(UITapGestureRecognizer.init(target:action:)),
#selector(gesture.gh_init(target:action:))
],
[
#selector(gesture.addTarget(_:action:)),
#selector(gesture.gh_addTarget(_:action:))
],
]
for item in selectors {
let originalSelector: Selector = item[0]
let swizzledSelector: Selector = item[1]
let originalMethod: Method? = class_getInstanceMethod(gesture, originalSelector)
let swizzledMethod: Method? = class_getInstanceMethod(gesture, swizzledSelector)
if originalMethod == nil {
continue
}
let didAddMethod: Bool = class_addMethod(gesture, originalSelector, method_getImplementation(swizzledMethod!), method_getTypeEncoding(swizzledMethod!))
if didAddMethod {
class_replaceMethod(gesture, swizzledSelector, method_getImplementation(originalMethod!), method_getTypeEncoding(originalMethod!))
} else {
method_exchangeImplementations(originalMethod!, swizzledMethod!)
}
}
}
extension UITapGestureRecognizer {
private static let dispatchOnceTime: Void = {
swizzle(UITapGestureRecognizer.self)
}()
@objc open class func startAOP() {
guard self === UITapGestureRecognizer.self else { return }
UITapGestureRecognizer.dispatchOnceTime
}
// MARK: 交换的方法
@objc func gh_init(target: Any?, action: Selector?) -> UIGestureRecognizer {
if target == nil {
return self.gh_init(target: target, action: action);
}
if (target as? UIResponder) == nil {
return self.gh_init(target: target, action: action);
}
// 初始化判断
if (target as? UIResponder)?.ghGestureActions == nil {
(target as? UIResponder)?.ghGestureActions = []
}
// 一个手势对应一个GHUITapGestureRecognizerAction属性，再由target去强制有所有的GHUITapGestureRecognizerAction
let ghAction = GHUITapGestureRecognizerAction()
ghAction.target = (target as? UIResponder)
ghAction.action = action
(target as? UIResponder)?.ghGestureActions?.append(ghAction)
return self.gh_init(target: ghAction, action: #selector(ghAction.ghGestureRecognizerAction(sender:)))
}
@objc func gh_addTarget(_ target: Any, action: Selector) {
if (target as? UIResponder) == nil {
return self.gh_addTarget(target, action: action);
}
if (target as? UIResponder)?.ghGestureActions == nil {
(target as? UIResponder)?.ghGestureActions = []
}
let ghAction = GHUITapGestureRecognizerAction()
ghAction.target = (target as? UIResponder)
ghAction.action = action
(target as? UIResponder)?.ghGestureActions?.append(ghAction)
return self.gh_addTarget(ghAction, action: #selector(ghAction.ghGestureRecognizerAction(sender:)))
}
}
很多第三方库也有功能强大的AOP逻辑，本文主要是轻量级的代码实现，其他第三方库暂不做介绍
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent