为什么NSDictionary是零？

Question

这是我正在做错误帮助的代码。

         for result in (result2 ){

            var dictData: NSDictionary?

             dictData?.setValue(result.valueForKey("offer_title") as? String, forKey:"offer_title")
              print(result.valueForKey("offer_title") as? String)
            if result.valueForKey("discountPercentageOff") as? String != "" {
                dictData?.setValue(result.valueForKey("discountPercentageOff") as? String, forKey:"discountPercentageOff")
                print(result.valueForKey("discountPercentageOff") as? String)
            }

            dictData?.setValue(result.valueForKey("is_booked") as? Bool, forKey:"is_booked")
             print(result.valueForKey("is_booked"))
            dictData?.setValue(result.valueForKey("is_saved") as? Bool, forKey:"is_saved")
            print(result.valueForKey("is_saved"))

            dictData?.setValue(result.valueForKey("area_id") as? String, forKey:"area_id")
            print(result.valueForKey("area_id"))

            dictData?.setValue(result.valueForKey("area_name") as? String, forKey:"area_name")

            dictData?.setValue(result.valueForKey("business_id") as? String, forKey:"business_id")
            dictData?.setValue(result.valueForKey("business_name") as? String, forKey:"business_name")
            dictData?.setValue(result.valueForKey("category_id") as? String, forKey:"category_id")
            dictData?.setValue(result.valueForKey("category_name") as? String, forKey:"category_name")
            dictData?.setValue(result.valueForKey("expiry_date") as? String, forKey:"expiry_date")
            dictData?.setValue(result.valueForKey("featured") as? String, forKey:"featured")
            dictData?.setValue(result.valueForKey("locality") as? String, forKey:"locality")
            dictData?.setValue(result.valueForKey("offer_available") as? String, forKey:"offer_available")
            dictData?.setValue(result.valueForKey("offer_id") as? String, forKey:"offer_id")
            dictData?.setValue(result.valueForKey("offer_image") as? String, forKey:"offer_image")
            dictData?.setValue(result.valueForKey("offer_nature") as? String, forKey:"offer_nature")
            dictData?.setValue(result.valueForKey("offerNatureValue") as? String, forKey:"offerNatureValue")
            dictData?.setValue(result.valueForKey("on_going") as? Bool, forKey:"on_going")
            dictData?.setValue(result.valueForKey("discountOriginalPrice") as? String, forKey:"discountOriginalPrice")
            dictData?.setValue(result.valueForKey("discountDiscountedPrice") as? String, forKey:"discountDiscountedPrice")

            let offer = Offer()
            offer.setDatafromServer(dictData!)
             self.saveOfferData(item as! NSDictionary)
            print("item:\(dictData)")

            self._featuredOfferArray.addObject(offer)
            self.feturedOfferTableView.reloadData()



        }

当我传递nsdictionary作为参数时，它给出了错误可选的nil，你可以看到我创建了每个循环的nsdictionary。 但它还没有。 我不明白。

Answer 1

 var dictData: NSDictionary?

将此行更改为

 var dictData = NSMutableDictionary();

Answer 2

你永远不会初始化你的字典， var dictData: NSDictionary? 只定义变量的类型。 此外，如果您想要更改字典，它必须是可变的。

从...开始：

var dictData: NSMutableDictionary? = NSMutableDictionary()

Answer 3

失败的原因是字典根本没有初始化。

使用Swift本机类型有一种更简单的语法，实际上不需要任何类型转换，因为您只是复制AnyObject项。 如果任何值为nil ，则不设置密钥。

 for result in result2  {

     var dictData = [String:AnyObject]()

     dictData["offer_title"] = result["offer_title"]
     dictData["discountPercentageOff"] = result["discountPercentageOff"]
...

甚至复制整个字典（在Swift中由于值语义而没有问题）并删除未使用的密钥仍然更有效。