如何在swift中检查JSON是否为null？

Question

我目前正在开发一个应用程序,它以下列格式返回json

"location_subtype"="somevalue"; "location_type"=强制; month ="2015-01"; "outcome_status"= {category ="somevalue"; date ="somevalue"; };

如果"outcome_status"具有值,则显示类别和日期,但是如果"outcome_value"没有任何值(在大多数情况下),则显示如下

"location_subtype"="somevalue"; "location_type"=强制; month ="2015-01"; "outcome_status"=""; "persistent_id"="";

问题是我如何检查outcome_status的值是否不是"null"？

我已经尝试了以下方法将类别和日期存储到标签中,但它会遇到错误,第一个if语句应该检查该值是否为null,如果它不是转到下一个if语句.然而,它继续下一个if语句,我得到以下错误

线程1:EXC_BAD_ACCESS(代码= 2,地址= 0x102089600)

if (dict["outcome_status"] != nil)
        {
            if ((dict["outcome_status"]as NSDictionary)["category"] != nil)
            {
                outcomeStatusLabel.text = ((dict["outcome_status"]as NSDictionary)["category"] as NSString)
                outcomeStatusLabel.font = UIFont.systemFontOfSize(14.0);
                outcomeStatusLabel.numberOfLines = 0
            }

            if ((dict["outcome_status"]as NSDictionary)["date"] != nil)
            {
                outcomeDateLabel.text = ((dict["outcome_status"]as NSDictionary)["date"] as NSString)
                outcomeDateLabel.font = UIFont.systemFontOfSize(14.0);
                outcomeDateLabel.numberOfLines = 0
            }
        }

如果我删除第一个if语句,它只会在"outcome_status"="null"时崩溃,并且如果"outcome_status"中有一些值则完全正常

我需要做什么,如果值为null,它会在1st if语句处停止？

先感谢您.

Answer 1

尝试这样的事情:

SWIFT代码:

if let outcome = dict["outcome_status"] as? NSDictionary {
    //Now you know that you received a dictionary(another json doc) and is not 'nil'
    //'outcome' is only valid inside this if statement

    if let category = outcome["category"] as? String {
        //Here you received string 'category'
        outcomeStatusLabel.text = category
        outcomeStatusLabel.font = UIFont.systemFontOfSize(14.0)
        outcomeStatusLabel.numberOfLines = 0
    }

    if let date = outcome["date"] as? String {
        //Here you received string 'date'
        outcomeDateLabel.text = date
        outcomeDateLabel.font = UIFont.systemFontOfSize(14.0)
        outcomeDateLabel.numberOfLines = 0
    }
}

这是与Json合作的安全方式.

Answer 2

if ((nullObject as? NSNull) == nil)  {
        ...
       }

Answer 3

如果您使用的是 Alamofire 和 JSONSubscriptType，请使用：

if !(parsedJSON["someKey"] == JSON.null) {
//do your stuff 
}