线程3：致命错误：索引超出范围

Question

I am trying to make to extract weather data but I get an out of range error. can anyone help? My friend told me its a problem with my array but I was sure to use a string separator.

My main goal is to retrieve the weather data from the website and then add it to a variable called message

override func viewDidLoad() {
    super.viewDidLoad()
    let url = URL(string: "https://weather.weatherbug.com/weather-forecast/now/salt-lake-city")!
    let request = NSMutableURLRequest(url: url)

    let task = URLSession.shared.dataTask(with: request as URLRequest){
        data, response, error in

        var message = ""
        if  error != nil{
            print(error.debugDescription)
        }else{
            if let unwrappedData = data {
                let dataString = NSString(data: unwrappedData, encoding: String.Encoding.utf8.rawValue)

                var stringSeperator = "<span class=\"value ng-binding ng-scope\" ng-if=\"widget.ObservationAggregate.Observation.FeelsLike\" ng-bind=\"UnitUtility.convertTemp(widget.ObservationAggregate.Observation.FeelsLike)\">"

                if let contentArray = dataString?.components(separatedBy: stringSeperator){
                    if contentArray.count > 0 {
                       stringSeperator = "</span>"

                       let newContentArray = contentArray[1].components(separatedBy: stringSeperator)

                       if newContentArray.count > 0 {
                           message = newContentArray[0]
                           print(newContentArray[0])
                       }
                    }
                }
            }
        }
    }

    task.resume()
}

Answer 1

I'm assuming that you are getting this error on the following line.

let newContentArray = contentArray[1].components(separatedBy: stringSeperator)

The problem seems to be that you are checking your contentArray 's count to be greater than 0 but accessing index 1. Note here that an array's count being not 0 does not necessitate that it will have a value at index 1. Since the array's index start with 0, index 1 would in fact require your array's count to be at least 2.

Answer 2

When we want to get some info from a server it is recommended to get/parse a JSON or an XML . I see you are trying to parse an HTML from a website.

After clarifying that, if you don't have alternatives, I think you are reaching to those error: Index out of range since you are assuming your data will have always the format you think (normally you need to handle special cases)

You could update your internal validation to this:

if contentArray.count > 1 {
         stringSeperator = "</span>"
         let newContentArray = contentArray[1].components(separatedBy: stringSeperator)
         if newContentArray.count > 0 {
            message = newContentArray.first
            print(newContentArray.first)
         }
}

You can group those if in a better way but this is just to guide you.

I hope this helps you.