I have a basic question to convert string to number in Swift. I found a good stack overflow question that helps me convert a JSON string to a number, but I get an error when I try to add or subtract the values.
I am sure I am missing something obvious!
Phil
Error: Referencing operator function '-' on 'BinaryInteger' requires that 'NSNumber' conform to 'BinaryInteger'
func red2G()->String {
let numberFormatter = NumberFormatter()
// Prev Close
let number1 = numberFormatter.number(from: pricesAlpha?.globalQuote.prevClose ?? "0.000")
if let final1 = number1?.floatValue {
print("Returned number is " + String(format: "%.2f", final1))
}
// Open
let number2 = numberFormatter.number(from: pricesAlpha?.globalQuote.open ?? "0.000")
if let final2 = number2?.floatValue {
print("Returned number is " + String(format: "%.2f", final2))
}
// Price
let number3 = numberFormatter.number(from: pricesAlpha?.globalQuote.price ?? "0.000")
if let final3 = number3?.floatValue {
print("Returned number is " + String(format: "%.2f", final3))
}
return String(number3-number2)
}
I simplified the function based on the proposed answer:
func load(symbolName:String) {
self.symbolName = symbolName
}
func red2G()->String {
let numberFormatter = NumberFormatter()
// Prev Close
let prevClose = numberFormatter.number(from: pricesAlpha?.globalQuote.prevClose ?? "0.000")?.floatValue
// Open
let openPrice = numberFormatter.number(from: pricesAlpha?.globalQuote.open ?? "0.000")?.floatValue
// Price
let currentPrice = numberFormatter.number(from: pricesAlpha?.globalQuote.price ?? "0.000")?.floatValue
return String((openPrice ?? 0.00) - (prevClose ?? 0.00) - (currentPrice ?? 0.00))
}
The values are based on this JSON Dictionary
struct GlobalQuote: Codable {
let globalQuote: PriceAlpha
enum CodingKeys : String, CodingKey {
case globalQuote = "Global Quote"
}
}
struct PriceAlpha: Codable {
let symbol: String
let open: String
let high: String
let low: String
let price: String
let volume: String
let tradingDay: String
let prevClose: String
let change: String
let pctChange: String
enum CodingKeys : String, CodingKey {
case symbol = "01. symbol"
case open = "02. open"
case high = "03. high"
case low = "04. low"
case price = "05. price"
case volume = "06. volume"
case tradingDay = "07. latest trading day"
case prevClose = "08. previous close"
case change = "09. change"
case pctChange = "10. change percent"
}
}
NSNumber
is a object wrapper around an actual integer or float or whatever. You see in your code where you call floatValue
? That gets an actual number that you can do math with. Keep final3
and final2
around outside of their if
statements and do the math on that.
That said, you should almost certainly implement custom decoding and encoding in PriceAlpha
so that the struct already contains values in the correct semantic type (eg Float
) instead of String
. But for financial information, you'll actually want Decimal
, not Float
.
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