EXC_BAD_INSTRUCTION 检查 xml 元素在 swift 中是否为空时出错

Question

我在检查 xml 元素是否有 desire 标签时遇到问题：

我写了如下代码：

//checking if link is empty
if xml["rss"]["channel"]["item"][index]["source"].element!.attributes["url"] != "" {
   Link = (xml["rss"]["channel"]["item"][index]["source"].element?.attributes["url"])!
 } else {
     Link = ""
 }

当我运行这段代码时，我的代码第一行出现错误：Thread3 EXC_BAD_INSTRUCTION，但是当我运行时，代码如下：如果不理解源元素根本不存在，它就会通过！代码：

 //checking if link is empty
  if (xml["rss"]["channel"]["item"][index]["source"].element?.attributes["url"] as String?) != nil {
     Link = (xml["rss"]["channel"]["item"][index]["source"].element?.attributes["url"] as String?)!
   } else {
         Link = ""
   }

如何检查 swift 2 中是否存在源元素？

完整代码：

let xml = SWXMLHash.parse(data)

//one root element
let count = xml["rss"]["channel"]["item"].all.count
print(count)

var Name = ""
var Image = ""
var Link = ""
var Time = ""

for var index = 0; index < count; index++ {
    Name = xml["rss"]["channel"]["item"][index]["title"].element!.text!
    Image = (xml["rss"]["channel"]["item"][index]["description"]["img"].element?.attributes["src"])!

    //checking if time is empty
    if let check_time = xml["rss"]["channel"]["item"][index]["pubDate"].element?.text! as String? {
        Time = check_time
    }else{
        Time = ""
    }

    //checking if link is empty
    if let element = xml["rss"]["channel"]["item"][index]["source"].element?.attributes["url"] as String? where element != "" {
        print("salalalalam")
        print(Link)
        Link = element
    } else {
        Link = ""
    }

Answer 1

在您的第一个片段中，元素似乎为 nil，因此您的代码崩溃了。在你的第二个片段中（因为元素是零）它只是通过了低谷。

如何在 Swift 中使用条件可选绑定？

let i:[Int?] = [1,2,10, nil]
i.forEach { v in
    if let x = v where x != 10 {
        print("value passed the test:", x)
    } else {
        print("didn't  pass the test:", v)
    }
}
/*
value passed the test: 1
value passed the test: 2
didn't  pass the test: Optional(10)
didn't  pass the test: nil
*/

根据您的笔记进行更新

if let url = xml["rss"]["channel"]["item"][index]["source"].element?.attributes["url"] {
    Link = url 
} else {
    Link = ""
}

EXC_BAD_INSTRUCTION 检查 xml 元素在 swift 中是否为空时出错

EXC_BAD_INSTRUCTION error for checking if xml element is empty in swift

xml

if-statement

ios

is-empty

swift2