1、本人使用swift4.1，弄了一晚上才弄好，结果还是一个小问题真是尴尬， 要在model中每个属性前面加上@objc

import UIKit

classUserModel: NSObject {

  @objc var dix = String()

}

 let dic = ["dix":"ffffff"] as NSDictionary

        let model =UserModel.mj_object(withKeyValues: dic)!

        print(model.dix)