关联属性
创建Person类，然后在扩展文件里面添加address属性。
代码语言：javascript复制class Person: NSObject {
@objc private var name: String = ""
@objc private var gender: String = ""
}
var ADDRESSKEY = "ADDRESSKEY"
extension Person {
/// Extension里面添加属性
var address: String? {
set {
objc_setAssociatedObject(self, &ADDRESSKEY, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN)
}
get {
return objc_getAssociatedObject(self, &ADDRESSKEY) as? String
}
}
}
p.address = "YiShanLu No.404"
debugPrint(p.address!)
=================print=======================
"YiShanLu No.404"
