arrays - How to get substring out of string in swift ui?

Question

In UIKit I used the same method to get only one part out of a long string and there it worked. However it dosen't work in swift ui app. I have wondered if it might be that it is not a string, but something else. Does anyone know a better solution to only get a short substring out of the long text?

let url = URL(string: "https://midcdmz.nrel.gov/apps/spa.pl?syear=2020&smonth=1&sday=1&eyear=2020&emonth=1&eday=1&otype=0&step=60&stepunit=1&hr=12&min=0&sec=0&latitude=39.743&longitude=-105.178&timezone=-7.0&elev=1829&press=835&temp=10&dut1=0.0&deltat=64.797&azmrot=180&slope=0&refract=0.5667&field=0")

struct ContentView: View {
    
    
    var html = try! String(contentsOf: url!, encoding: String.Encoding.ascii)
    
    let leftSideOfTheValue = "1/1/2020,0:00:00,"
    
    let rightSideOfTheValue = "1/1/2020,1:00:00,"
    
    guard let leftRange = html.range(of: leftSideOfTheValue) else {
        print("cant find left range")
        return
    }
    
    guard let rightRange = html.range(of: rightSideOfTheValue) else {
        print("cant find right range")
        return
    
    let rangeOfTheValue = leftRange.upperBound..<rightRange.lowerBound
    
    let elevationInfo = (html[rangeOfTheValue])
    
    var body: some View {
        Text(elevationInfo)
                
    }

Answer 1

The question is not particularly related to Swift UI, the following solution is general.

As I said a few times the received data is CSV (comma separated values), each line is a record, the fields are separated by comma.

To parse the string first create a custom struct

struct ZenithData {
    let date : Date
    let angle : Double
}

and a data source array

var zenithData = [ZenithData]()

then load the data asynchronously with URLSession, split the text into lines, split the lines into fields, join the date and time parts and convert it into Date and populate the array.

Note: The exact date format is ambiguous. The format could be also d/M/yyyy

let url = URL(string: "https://midcdmz.nrel.gov/apps/spa.pl?syear=2020&smonth=1&sday=1&eyear=2020&emonth=1&eday=1&otype=0&step=60&stepunit=1&hr=12&min=0&sec=0&latitude=39.743&longitude=-105.178&timezone=-7.0&elev=1829&press=835&temp=10&dut1=0.0&deltat=64.797&azmrot=180&slope=0&refract=0.5667&field=0")

let dataTask = URLSession.shared.dataTask(with: url!) { data, _, error in
    if let error = error { print(error); return }
    let string = String(data: data!, encoding: .utf8)!
    let dateFormatter = DateFormatter()
    dateFormatter.locale = Locale(identifier: "en_US_POSIX")
    dateFormatter.dateFormat = "M/d/yyyy H:mm:ss"
    
    let lines = string.components(separatedBy: CharacterSet.newlines)
    for i in 1..<lines.count { // first line is dropped
        let fields = lines[i].components(separatedBy: ",")
        if fields.count != 3 { continue }
        let date = dateFormatter.date(from: fields[0] + " " + fields[1])!
        let angle = Double(fields[2])!
        zenithData.append(ZenithData(date: date, angle: angle))
    }
    print(zenithData)
}
dataTask.resume()