1. 注意后台json返回的同一字段返回数据不一样问题，导致Mapper属性为nil
   常见的是 后台的int和String类型被混用了,{"errorCode": 1002}和{"errorCode": "1002"}

自定义兼容int和string的转化
let transformInt = TransformOf<Int, String>(fromJSON: { (value: Any) -> Int? in
// transform value from String? to Int?
if let rs = value as? Int{
return rs
}else if let rs = value as? String{
return Int(rs)
}else{
return Int.max
}

}, toJSON: { (value: Int?) -> String? in
// transform value from Int? to String?
if let value = value {
return String(value)
}
return nil
})