以下是发生异常的代码

import UIKit
extension NSObject {

    // MARK: - 定义一个类属性作为闭包容器
    class XYPropertyBlockContainer {

        var viewModelBlock : ViewModelBlock?
        
        var viewMangerInfosBlock : ViewMangerInfosBlock?

        var viewModelInfosBlock : ViewModelInfosBlock?
        
    }
}

问题描述：

Swift项目中再给NSobject类extension中添加类属性作为闭包容器后，在外界创建给这个闭包容器赋值时，发生奔溃，异常内容如下：

*** NSForwarding: warning: object 0x17027acc0 of class '_TtCE10MVVMExapleCSo8NSObject24XYPropertyBlockContainer' does not implement methodSignatureForSelector: -- trouble ahead
Unrecognized selector -[_TtCE10MVVMExapleCSo8NSObject24XYPropertyBlockContainer copy]

问题分析：
1.通过异常信息可以发现是XYPropertyBlockContainer类未实现copy方法导致的，XYPropertyBlockContainer是我定义的闭包容器类
2.原因这个类我未让它继承自NSObject，当我让其继承自NSObjcet后，再次运行时，再报异常reason: '-[_TtCE10MVVMExapleCSo8NSObject24XYPropertyBlockContainer copyWithZone:]: unrecognized selector sent to instance
3.最后让XYPropertyBlockContainer类继承自NSObjcet且遵守NSCopying协议，重写copy(with zone: NSZone? = nil) -> Any方法解决

解决异常后的代码

import UIKit

extension NSObject {

    typealias ViewModelBlock = () -> Void
    typealias ViewMangerInfosBlock = () -> Void
    typealias ViewModelInfosBlock = () -> Void
    
    // MARK: - 定义一个类属性作为block容器
    class XYPropertyBlockContainer: NSObject, NSCopying {
   
        func copy(with zone: NSZone? = nil) -> Any {
            return self
        }
        
        var viewModelBlock : ViewModelBlock?
        var viewMangerInfosBlock : ViewMangerInfosBlock?
        var viewModelInfosBlock : ViewModelInfosBlock?

    }
    
    // MARK: - 关联属性的key
    private struct RunTimeKey {
        static let blockContainerKey = UnsafeRawPointer(bitPattern: "blockContainerKey".hashValue)
        static let viewMangerDelegateKey = UnsafeRawPointer(bitPattern: "viewMangerDelegate".hashValue)
        static let viewModelDelegateKey = UnsafeRawPointer(bitPattern: "viewModelDelegateKey".hashValue)
        static let xy_viewMangerInfosKey = UnsafeRawPointer(bitPattern: "xy_viewMangerInfosKey".hashValue)
        static let xy_viewModelInfosKey = UnsafeRawPointer(bitPattern: "xy_viewModelInfosKey".hashValue)
        static let xy_mediatorKey = UnsafeRawPointer(bitPattern: "xy_mediatorKey".hashValue)
    }

    /// 闭包容器属性
    var propertyBlockContainer : XYPropertyBlockContainer? {
        set {
            objc_setAssociatedObject(self, RunTimeKey.blockContainerKey, newValue, .OBJC_ASSOCIATION_COPY_NONATOMIC)
        }
        
        get {
            if let blockContainer = objc_getAssociatedObject(self, RunTimeKey.blockContainerKey) as? XYPropertyBlockContainer {
            
                return blockContainer
            }
            return nil
        }
    }
}

注意：外界给闭包容器中的闭包赋值或者调用时，需要先创建闭包容器

@IBAction func btnClick(_ sender: Any) {
        // 传递事件 通过闭包
        if self.propertyBlockContainer == nil {
            self.propertyBlockContainer = XYPropertyBlockContainer()
            self.propertyBlockContainer?.viewModelInfosBlock = {
                print("1+2")
            }
            self.propertyBlockContainer?.viewModelBlock = {
                print("1+3")
            }
            self.propertyBlockContainer?.viewMangerInfosBlock = {
                print("1+4")
            }
            
            self.propertyBlockContainer?.viewMangerInfosBlock!()
            self.propertyBlockContainer?.viewModelBlock!()
            self.propertyBlockContainer?.viewModelInfosBlock!()
        }