iOS原理之Category的关联对象

import UIKit 
//类似于hash表
class CustomMutableDictionary: NSObject {
    var dict:NSMutableDictionary?
    
    override init() {
        super.init()
        dict = NSMutableDictionary()
    }
  
    func setObject(_ anObject: Any?, forKey aKey: NSCopying) { 
        dict?.setValue(anObject, forKey: aKey as! String)
    }
    func object(forKey aKey: Any) -> Any? {
        return dict?.value(forKey: aKey as! String)
    }
}

//
//  ObjcReference.swift
//  iOS底层
//
//  Created by yanqunchao on 2019/5/18.
//  Copyright © 2019 yanqunchao. All rights reserved.
//

import UIKit

enum AccociationPolicy:Int {
    case OBJC_ASSOCIATION_ASSIGN = 0
    case OBJC_ASSOCIATION_RETAIN_NONATOMIC = 1
    case OBJC_ASSOCIATION_COPY_NONATOMIC = 2
}

class ObjcReference: NSObject {
    //对象关联者
    class ObjcAssociation: NSObject {
        var value:Any?   //关联的值
        var policy: AccociationPolicy?  //关联的策略
    }
    
    //关联对象表
    class ObjectAssociationMap: CustomMutableDictionary {
        
        
      
        // key    refs:Int?  //对象关联属性的标记
        // value  objectAsscociate: ObjcAssociation? //与属性标记对应的关联者
    }
    
    //关联者哈希表
    class AssociationsHashMap: CustomMutableDictionary {
        //        key disguised_ptr_t:Int?  //存放关联对象的地址
        //        value objectAsscociateMap: ObjectAssociationMap?  //与对象地址对应的关联对象表
    }
    
    
    /**
     * 全局关联对象管理者
     */
    class AssociationsManager: NSObject {
        static let map: AssociationsHashMap =  AssociationsHashMap()
    }
    
    //为某个对象的某个属性关联值
    static func objectSetAssociativeReference(object: AnyObject, key: String, value: Any?, policy: AccociationPolicy) {
        
        let map = AssociationsManager.map

        
        let keyAddr = Unmanaged.passUnretained(object as AnyObject).toOpaque()
        let keyAddrStr = "\(keyAddr)"
      
        //先找object对应的map
        var objectAsscociationMap = map.object(forKey: keyAddrStr) as? ObjectAssociationMap
        
        if objectAsscociationMap == nil { //如果没有找到，创建一个map
            objectAsscociationMap = ObjectAssociationMap()
        }
      
        if value == nil { //设置的值为空
            objectAsscociationMap!.setObject(nil, forKey: key as NSCopying)
        }else{
            let objcAssociation = ObjcAssociation()
            objcAssociation.value = value
            objcAssociation.policy = policy
            objectAsscociationMap!.setObject(objcAssociation, forKey: key as NSCopying)
        }
        
        map.setObject(objectAsscociationMap, forKey: keyAddrStr as NSCopying)
        
     }
    //获取某个对象的某个属性
    static func objectGetAssociativeReference(object: AnyObject, key: String) -> Any?{
        
        let map = AssociationsManager.map
        
        
        let keyAddr = Unmanaged.passUnretained(object as AnyObject).toOpaque()
        let keyAddrStr = "\(keyAddr)"
         
        guard  let objectAsscociationMap = map.object(forKey: keyAddrStr) as? ObjectAssociationMap  else {
            return nil
        }

        
        guard  let objcAssociation = objectAsscociationMap.object(forKey: key) as? ObjcAssociation
            else {
            return nil
        }
        
        return objcAssociation.value
    }
    
    //移除某个对象的所有关联属性
    
    static func objectRemoveAssocations(object: AnyObject) {
        
        let map = AssociationsManager.map
        
        let keyAddr = Unmanaged.passUnretained(object as AnyObject).toOpaque()
        let keyAddrStr = "\(keyAddr)"
        
        guard  (map.object(forKey: keyAddrStr) as? ObjectAssociationMap) != nil  else {
            
            return
        }
        
        map.setObject(nil, forKey: keyAddrStr as NSCopying)
    }
}

//
//  CategoryBasementAssociateObjectViewController.swift
//  iOS底层
//
//  Created by yanqunchao on 2019/5/18.
//  Copyright © 2019 yanqunchao. All rights reserved.
//

import UIKit
///关联对象
class CategoryBasementAssociateObjectViewController: UIViewController {
 
    class Category1: NSObject {
        
        
        var name:String? {
            get{
                return (ObjcReference.objectGetAssociativeReference(object: self, key: "name") as? String) ?? ""
            }
            set{
                ObjcReference.objectSetAssociativeReference(object: self, key: "name", value: newValue, policy: AccociationPolicy.OBJC_ASSOCIATION_COPY_NONATOMIC)
            }
        }
        
        var number:String? {
            get{
                return (ObjcReference.objectGetAssociativeReference(object: self, key: "number") as? String) ?? ""
            }
            set{
                 ObjcReference.objectSetAssociativeReference(object: self, key: "number", value: newValue, policy: AccociationPolicy.OBJC_ASSOCIATION_COPY_NONATOMIC)
            }
        }
    }
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .white
        
     
        let category1 = Category1()
        category1.name = "小明"
        category1.number = "12345"
        
        let category2 = Category1()
        category2.name = "小明2"
        category2.number = "67890"
        
        print(category1.name ?? "")
        print(category1.number ?? "")
        
        print(category2.name ?? "")
        print(category2.number ?? "")
        
        category1.name = nil
        
        print(category1.name ?? "")
        
        
        //调用结束时，清除关联对象
        ObjcReference.objectRemoveAssocations(object: category1)
        ObjcReference.objectRemoveAssocations(object: category2)
        
    }
}