I'm taking data from an api and storing it in a string variable. When I print the variable it returns what I'm looking for but when I try to convert it to an int using the .toInt method it returns a nil?
func getWeather() {
let url = NSURL(string: "http://api.openweathermap.org/data/2.5/weather?q=London&mode=xml")
let task = NSURLSession.sharedSession().dataTaskWithURL(url!) {
(data, response, error) in
if error == nil {
var urlContent = NSString(data: data, encoding: NSUTF8StringEncoding) as NSString!
var urlContentArray = urlContent.componentsSeparatedByString("temperature value=\"")
var temperatureString = (urlContentArray[1].substringWithRange(NSRange(location: 0, length:6))) as String
println(temperatureString) // returns 272.32
var final = temperatureString.toInt()
println(final) //returns nil
println(temperatureString.toInt())
self.temperature.text = "\(temperatureString)"
}
}
task.resume()
}
Even simpler, though slightly a trick, you can use integerValue:
temperatureString.integerValue
Unlike toInt, integerValue will stop converting when it finds a non-digit (it also throws away leading spaces.
If temperatureString is a String (rather than an NSString), you'll need to push it over:
(temperatureString as NSString).integerValue
That's because 272.32 is not an integer.
You could convert it to a Float.
272.32 isn't an Integer. If your temperature string is an NSString, you can do this to convert it:
Int("272.32".floatValue)
Related
I am having difficulty in converting an Int32 to String. I tried to following:
String(cartItem?.quantity)
"\(cartItem?.quantity)"
but no luck.
cart.quantity is of type Int32.
quantity is an attribute of cart in the CoreData model.
The question isn't clear but what I think this issue boils down to is that you can't init a string with an optional value.
So either do as #matt suggested and force unwrap the cartItem
String(cartItem!.quantity)
or supply a default value
String(cartItem?.quantity ?? 0)
Of course if you need to handle the fact that you might not have a cart then it is better to do it like
if let cart = cartItem {
let str = "\(cart.quantity)" //or String(cart.quantity)
//do stuff with str
} else {
//handle no cart state
}
you can by declare string and data
var arrayOf32Int: [UInt32] = [1,32,100,984,13,542]
let data = Data(bytes: arrayOf32Int, count: arrayOf32Int.count * MemoryLayout<UInt32>.stride)
let string = String(data: data, encoding: .utf32LittleEndian)!
print(string)
I check the optional string
print(limitCash)
if let value = Int32(limitCash) {
aProvider.limitBuy = value
}
The value of limitCash is Optional("500").
The program checks if let statement and skips it without assigning value.
Program crashes if I try aProvider.limitBuy = Int32(limitCash)!
First you need to unwrap String? to String and then unwrap the result of casting from String to UInt32 (that will be Uint32?).
print(limitCash)
if let stringValue = limitCash {
if let value = Int32(stringValue) {
print(value) // 500
}
}
I want to decode my nsData to a String Array. I have this code right now:
func nsDataToStringArray(data: NSData) -> [String] {
var decodedStrings = [String]()
var stringTerminatorPositions = [Int]()
var currentPosition = 0
data.enumerateBytes() {
buffer, range, stop in
let bytes = UnsafePointer<UInt8>(buffer)
for i in 0 ..< range.length {
if bytes[i] == 0 {
stringTerminatorPositions.append(currentPosition)
}
currentPosition += 1
}
}
var stringStartPosition = 0
for stringTerminatorPosition in stringTerminatorPositions {
let encodedString = data.subdata(with: NSMakeRange(stringStartPosition, stringTerminatorPosition - stringStartPosition))
let decodedString = NSString(data: encodedString, encoding: String.Encoding.utf8.rawValue)! as String
decodedStrings.append(decodedString)
stringStartPosition = stringTerminatorPosition + 1
}
return decodedStrings
}
But I get an error on this line: let bytes = UnsafePointer<UInt8>(buffer)
Cannot invoke initializer for type 'UnsafePointer' with an
argument list of type '(UnsafeRawPointer)'
Do I need to convert the buffer to a UnsafePointer? If so, how can I do that?
buffer in the enumerateBytes() closure is a UnsafeRawPointer
and you have to "rebind" it to an UInt8 pointer in Swift 3:
// let bytes = UnsafePointer<UInt8>(buffer)
let bytes = buffer.assumingMemoryBound(to: UInt8.self)
But why so complicated? You can achieve the same result with
func nsDataToStringArray(nsData: NSData) -> [String] {
let data = nsData as Data
return data.split(separator: 0).flatMap { String(bytes: $0, encoding: .utf8) }
}
How does this work?
Data is a Sequence of UInt8, therefore
split(separator: 0) can be called on it, returning an array of
"data slices" (which are views into the source data, not copies).
Each "data slice" is again a Sequence of UInt8, from which a
String can be created with String(bytes: $0, encoding: .utf8).
This is a failable initializer (because the data may be invalid UTF-8).
flatMap { ... } returns an array with all non-nil results,
i.e. an array with all strings which could be created from
valid UTF-8 code sequences between zero bytes.
i'm trying to create a simple user input but the only function that i have found in swift is this one
func input() -> String {
var keyboard = NSFileHandle.fileHandleWithStandardInput()
var inputData = keyboard.availableData
return NSString(data: inputData, encoding:NSUTF8StringEncoding) as String!
}
then i'm trying to convert input() to an Int for a mathematic operation (i'm using 1 as the input) with this
var inputToInt = input().toInt()!
in this point i get only nil i don't know what to do.
Swift 2.0 has a function called readLine() - using it is a much better idea than rolling your own.
http://swiftdoc.org/swift-2/func/readLine/
Your conversion to Int fails because the string contains newline. You can use this to clean it up:
let s = NSString(data: inputData, encoding:NSUTF8StringEncoding) as String!
if s.hasSuffix("\n") {
return s.substringToIndex(x.endIndex.predecessor())
} else {
return s
}
I considered a lot of similar questions, but still can't get the compiler to accept this.
Socket Mobile API (in Objective-C) passes ISktScanDecodedData into a delegate method in Swift (the data may be binary, which I suppose is why it's not provided as string):
func onDecodedData(device: DeviceInfo?, DecodedData d: ISktScanDecodedData?) {
let symbology: String = d!.Name()
let rawData: UnsafePointer<UInt8> = d!.getData()
let rawDataSize: UInt32 = decoded!.getDataSize()
// want a String (UTF8 is OK) or Swifty byte array...
}
In C#, this code converts the raw data into a string:
string s = Marshal.PtrToStringAuto(d.GetData(), d.GetDataSize());
In Swift, I can get as far as UnsafeArray, but then I'm stuck:
let rawArray = UnsafeArray<UInt8>(start: rawData, length: Int(rawDataSize))
Alternatively I see String.fromCString and NSString.stringWithCharacters, but neither will accept the types of arguments at hand. If I could convert from UnsafePointer<UInt8> to UnsafePointer<()>, for example, then this would be available (though I'm not sure if it would even be safe):
NSData(bytesNoCopy: UnsafePointer<()>, length: Int, freeWhenDone: Bool)
Is there an obvious way to get a string out of all this?
This should work:
let data = NSData(bytes: rawData, length: Int(rawDataSize))
let str = String(data: data, encoding: NSUTF8StringEncoding)
Update for Swift 3:
let data = Data(bytes: rawData, count: Int(rawDataSize))
let str = String(data: data, encoding: String.Encoding.utf8)
The resulting string is nil if the data does not represent
a valid UTF-8 sequence.
How about this, 'pure' Swift 2.2 instead of using NSData:
public extension String {
static func fromCString
(cs: UnsafePointer<CChar>, length: Int!) -> String?
{
if length == .None { // no length given, use \0 standard variant
return String.fromCString(cs)
}
let buflen = length + 1
var buf = UnsafeMutablePointer<CChar>.alloc(buflen)
memcpy(buf, cs, length))
buf[length] = 0 // zero terminate
let s = String.fromCString(buf)
buf.dealloc(buflen)
return s
}
}
and Swift 3:
public extension String {
static func fromCString
(cs: UnsafePointer<CChar>, length: Int!) -> String?
{
if length == nil { // no length given, use \0 standard variant
return String(cString: cs)
}
let buflen = length + 1
let buf = UnsafeMutablePointer<CChar>.allocate(capacity: buflen)
memcpy(buf, cs, length)
buf[length] = 0 // zero terminate
let s = String(cString: buf)
buf.deallocate(capacity: buflen)
return s
}
}
Admittedly it's a bit stupid to alloc a buffer and copy the data just to add the zero terminator.
Obviously, as mentioned by Zaph, you need to make sure your assumptions about the string encoding are going to be right.