I have converted a double to a string as I think it would be easier to manipulate. I have a string of: 14.52637472 for example.
How can I split it up into 2 variables, one for before the period, and one for ONLY 2 DECIMALS after?
so it should be: one = 14 and two = 52
This is my code to convert into a string: var str: String = all.bridgeToObjectiveC().stringValue
I don't know objective C, so I wouldn't really be able to do it that way, and I have read over the swift book on strings, but it does not discuss how to do this, or atleast I could not find that part?
Please would you help me out, want to build the app for my father to surprise him.
Start with the double, use NSString's format: initializer coupled with a format specifier to trim all but the tenths and hundredths column, and convert to string. Then use NSString's componentsSeparatedByString() to create a list of items separated by the period.
let theNumber = 14.52637472
let theString = NSString(format: "%.2f", theNumber)
let theList = theString.componentsSeparatedByString(".")
let left = theList[0] as String // Outputs 14
let right = theList[1] as String // Outputs 53
As second option using NSNumberFormatter.
let decimalNumber = NSDecimalNumber(double: 14.52637472)
let numberFormatter = NSNumberFormatter()
numberFormatter.maximumIntegerDigits = 2
numberFormatter.maximumFractionDigits = 2
let stringValue = numberFormatter.stringFromNumber(decimalNumber)
let theList = stringValue.componentsSeparatedByString(".")
Related
I am getting some coordinates from server in string array. And I am trying to save those coordinates in SQLite Database by splitting and converting them to double value. But some coordinates are getting saved in scientific notations. For example I am getting the following coordinate from server:
"-0.0000558,51.3368066"
I am splitting the string and converting it to double resulting in the following values:
[-5.58e-05,51.3368066]
I have tried following solutions but still returning same result:
1.
Double(latLongArr[0])
extension String{
var doubleValue: Double? {
return NumberFormatter().number(from: self)?.doubleValue
}
}
extension String{
var doubleValue: Double? {
let numberFormatter = NumberFormatter()
numberFormatter.allowsFloats = true
numberFormatter.maximumFractionDigits = 10
numberFormatter.numberStyle = .decimal
return numberFormatter.number(from: "\(self)")!.doubleValue
}
}
I have used the above code but it still returns in scientific format but I need it in normal decimal format. So what is the issue?
The last option is the option I would go for and I believe it works right.
I believe your issue is only when you print to console:
As you can see, the double variable is actually converted properly but just when it is formatted to print to the console it shows it as a scientific notation string.
Your other option besides using doubleValue is to use decimalValue
I suggest putting a breakpoint and checking the actual value of your double than reviewing it from the console output which is a formatted string.
Just for reference, code used in the image above:
let number = "-0.0000558"
let numberFormatter = NumberFormatter()
numberFormatter.numberStyle = .decimal
numberFormatter.maximumFractionDigits = 10
let finalNumber = numberFormatter.number(from: number)
let decimalNumber = finalNumber!.decimalValue
let doubleNumber = finalNumber!.doubleValue
print(decimalNumber)
print(doubleNumber)
If you want to print your Doubles without scientific notation use
String(format: "%.7f", value).
Example:
let value = Double(3.141592)
print(String(format: "%.7", value)
will print 3.1415920.
I have used the below extension to represent scientific values in the decimal format.
extension String {
func getDecimalValue() -> Decimal{
return NSNumber(value: Double(self)!).decimalValue
}
}
Usage:
let numberString = "+5.58e-05"
print(numberString.getDecimalValue()) //0.0000558
Objective-C code:
NSString *str = #"hi";
NSString *strDigit = #"1934"; (or #"193" may be a 3 digit or 4 digit value)
[dayText appendFormat:#"%#%4s,str,[strDigit UTF8String]];
The Objective-C code handles the output string with current alignment when it appears with 3 or 4 digits as output. It is correctly aligning to left and doesn't matter how much digits it is. Any one know how to handle this in Swift?
In Swift I tried with below code and the string is not adjusting the alignment according to the number of digits.
textForTrip += "\(str) \(String(format:"%4s", (strDigit.utf8))"
The %s format expects a pointer to a (NULL-terminated) C string
as argument, that can be obtained with the withCString method.
This would produce the same output as your Objective-C code:
let str = "Hi"
let strDigit = "193"
let text = strDigit.withCString {
String(format: "%#%4s", str, $0)
}
print(text)
It becomes easier if you store the number as integer instead of a
string:
let str = "Hi"
let number = 934
let text = String(format: "%#%4d", str, number)
print(text)
Try this below approach, that might help you
let strDigit = "\("1934".utf8)" //(or #"193" may be a 3 digit or 4 digit value)
var dayText = "Hello, good morning."
dayText += "\(strDigit.prefix(3))"
I'm seeing some strange bugs in my iPhone app that I have narrowed down to my use of NSNumberFormatter.
A stripped down example...
In Xcode playground I have:
let numberFormatter = NSNumberFormatter()
//numberFormatter.numberStyle = .DecimalStyle - does not change behavior
let numberString = "546000.06"
let number: NSNumber = numberFormatter.numberFromString(numberString)!
print("number: \(number)")
let number1: NSNumber = NSDecimalNumber(string: numberString)
print("number1: \(number1)")
This is the output:
number: 546000.0600000001
number1: 546000.06
Note that setting the numberStyle to .DecimalStyle doesn't change anything.
This issue only happens for certain numeric values (for example, 8.03 is another one). I thought NSNumberFormatter was safe for this type of conversion and I haven't seen much noise about this issue on the internet so I want to assume it is something I am doing wrong.
Can anyone explain what I am seeing? Any help is very much appreciated!
It looks like there is an issue with NSNumberFormatter. There are certain values where this rounding error creeps up. In the XCode 7.2.1 playground, it shows up around 8.03.
One way that I've solved this is to round the decimal number. Since the difference is +/- a tiny amount, rounding to 4 fraction places should work. You can use various rounding modes. In this example I used RoundPlain.
var initialValue = NSDecimalNumber(string: "7")
let handler = NSDecimalNumberHandler(roundingMode: NSRoundingMode.RoundPlain, scale: 4, raiseOnExactness: false, raiseOnOverflow: false, raiseOnUnderflow: false, raiseOnDivideByZero: false)
let numberFormatter = NSNumberFormatter()
for index in 1...300 {
initialValue = initialValue.decimalNumberByAdding(0.01)
let stringValue = "\(initialValue)"
var number = numberFormatter.numberFromString(stringValue)
var decimalNumber: NSDecimalNumber = NSDecimalNumber(decimal: number!.decimalValue)
decimalNumber = decimalNumber.decimalNumberByRoundingAccordingToBehavior(handler)
print("stringValue = \(stringValue), decimalNumber = \(decimalNumber), number = \(number!)")
}
You are seeing a rounding error.
If you would like to display a number to the user with two fraction digits, set maximumFractionDigits:
let numberFormatter = NSNumberFormatter()
numberFormatter.maximumFractionDigits = 2
let firstNumber = NSNumber(float:546000.06)
let firstNumberString = numberFormatter.stringFromNumber(firstNumber)!
let secondNumber = NSNumber(float:5.1337)
let secondNumberString = numberFormatter.stringFromNumber(secondNumber)!
print("firstNumber: \(firstNumberString)")
print("secondNumber: \(secondNumberString)")
The output will be:
"firstNumber: 546000.06\n"
"secondNumber: 5.13\n"
If you try to parse a number from a string, then you are all set.
let thirdNumber = numberFormatter.numberFromString("546000.06")!
print("thirdNumber \(thirdNumber.className): \(thirdNumber)")
The last line prints the description of the object itself (w/ rounding error):
"thirdNumber __NSCFNumber: 546000.0600000001\n"
Update (2016-03-18)
You want to parse the following string:
let currencyString = "$546,000.06"
First, we create a formatter with a locale and .CurrencyStyle. Be aware that the locale depends on the string you try to parse and not on the system you are running on.
let currencyFormatter = NSNumberFormatter.init()
currencyFormatter.locale = NSLocale.init(localeIdentifier: "en_US")
currencyFormatter.numberStyle = .CurrencyStyle
We can now use the formatter to prase the string.
let currencyNumber = currencyFormatter.numberFromString(currencyString)!
You are now free to store this object, for example in CoreData. However, if you wan't to present the value to the user (or print it on the console), you have to use a NSNumberFormatter. If you print the object directly, the description (or debugDescription) of the object is used.
So, let's create another formatter to print the value of your NSNumber object:
let outputFormatter = NSNumberFormatter.init()
outputFormatter.maximumFractionDigits = 10
Using many fraction digits should print any possible rounding errors. But
print("Number: \(outputFormatter.stringFromNumber(currencyNumber)!)")
outputs the desired result:
"Number: 546000.06\n"
What you have seen is the result of the internal representation of an NSNumber object (with description/debugDescription).
I'm seeing some strange bugs in my iPhone app that I have narrowed down to my use of NSNumberFormatter.
A stripped down example...
In Xcode playground I have:
let numberFormatter = NSNumberFormatter()
//numberFormatter.numberStyle = .DecimalStyle - does not change behavior
let numberString = "546000.06"
let number: NSNumber = numberFormatter.numberFromString(numberString)!
print("number: \(number)")
let number1: NSNumber = NSDecimalNumber(string: numberString)
print("number1: \(number1)")
This is the output:
number: 546000.0600000001
number1: 546000.06
Note that setting the numberStyle to .DecimalStyle doesn't change anything.
This issue only happens for certain numeric values (for example, 8.03 is another one). I thought NSNumberFormatter was safe for this type of conversion and I haven't seen much noise about this issue on the internet so I want to assume it is something I am doing wrong.
Can anyone explain what I am seeing? Any help is very much appreciated!
It looks like there is an issue with NSNumberFormatter. There are certain values where this rounding error creeps up. In the XCode 7.2.1 playground, it shows up around 8.03.
One way that I've solved this is to round the decimal number. Since the difference is +/- a tiny amount, rounding to 4 fraction places should work. You can use various rounding modes. In this example I used RoundPlain.
var initialValue = NSDecimalNumber(string: "7")
let handler = NSDecimalNumberHandler(roundingMode: NSRoundingMode.RoundPlain, scale: 4, raiseOnExactness: false, raiseOnOverflow: false, raiseOnUnderflow: false, raiseOnDivideByZero: false)
let numberFormatter = NSNumberFormatter()
for index in 1...300 {
initialValue = initialValue.decimalNumberByAdding(0.01)
let stringValue = "\(initialValue)"
var number = numberFormatter.numberFromString(stringValue)
var decimalNumber: NSDecimalNumber = NSDecimalNumber(decimal: number!.decimalValue)
decimalNumber = decimalNumber.decimalNumberByRoundingAccordingToBehavior(handler)
print("stringValue = \(stringValue), decimalNumber = \(decimalNumber), number = \(number!)")
}
You are seeing a rounding error.
If you would like to display a number to the user with two fraction digits, set maximumFractionDigits:
let numberFormatter = NSNumberFormatter()
numberFormatter.maximumFractionDigits = 2
let firstNumber = NSNumber(float:546000.06)
let firstNumberString = numberFormatter.stringFromNumber(firstNumber)!
let secondNumber = NSNumber(float:5.1337)
let secondNumberString = numberFormatter.stringFromNumber(secondNumber)!
print("firstNumber: \(firstNumberString)")
print("secondNumber: \(secondNumberString)")
The output will be:
"firstNumber: 546000.06\n"
"secondNumber: 5.13\n"
If you try to parse a number from a string, then you are all set.
let thirdNumber = numberFormatter.numberFromString("546000.06")!
print("thirdNumber \(thirdNumber.className): \(thirdNumber)")
The last line prints the description of the object itself (w/ rounding error):
"thirdNumber __NSCFNumber: 546000.0600000001\n"
Update (2016-03-18)
You want to parse the following string:
let currencyString = "$546,000.06"
First, we create a formatter with a locale and .CurrencyStyle. Be aware that the locale depends on the string you try to parse and not on the system you are running on.
let currencyFormatter = NSNumberFormatter.init()
currencyFormatter.locale = NSLocale.init(localeIdentifier: "en_US")
currencyFormatter.numberStyle = .CurrencyStyle
We can now use the formatter to prase the string.
let currencyNumber = currencyFormatter.numberFromString(currencyString)!
You are now free to store this object, for example in CoreData. However, if you wan't to present the value to the user (or print it on the console), you have to use a NSNumberFormatter. If you print the object directly, the description (or debugDescription) of the object is used.
So, let's create another formatter to print the value of your NSNumber object:
let outputFormatter = NSNumberFormatter.init()
outputFormatter.maximumFractionDigits = 10
Using many fraction digits should print any possible rounding errors. But
print("Number: \(outputFormatter.stringFromNumber(currencyNumber)!)")
outputs the desired result:
"Number: 546000.06\n"
What you have seen is the result of the internal representation of an NSNumber object (with description/debugDescription).
I am getting values back from a web service that gives me back prices in a string format, this is put into a Dictionary, so I get prices back as "1.5000" for example, which is obviously 1.50 in currency. However for the life of me I cannot get anything to work in Swift to format this correctly. In most other languages you can do this in a couple of seconds, so I'm getting a bit frustrated with something that is so simple.
Here's my test code:
var testnumber = "1.5000"
let n = NSNumberFormatter()
n.numberStyle = NSNumberFormatterStyle.DecimalStyle
n.maximumFractionDigits = 2
n.minimumFractionDigits = 2
let returnNumber = n.numberFromString(testnumber)
println("Returned number is \(returnNumber)")
This prints out in debug "number is Optional(1.5)" not 1.50!
I have changed NSNumberFormatterStyle.DecimalStyle to NSNumberFormatterStyle.CurrencyStyle as I thought that may do it for me as the returned number is a currency anyway, but that gives me back in debug "Returned number is nil" - which is even more confusing to me!
I have tried using maximumIntegerDigits and minimumIntegerDigits, setting locales using n.locale = NSLocale.currentLocale(), setting formatWidth, setting paddingPosition and paddingCharacter but nothing helps, I either get nil back to 1.5.
All I ultimately need to do is convert a string to a float or a currency value, and ensure there are 2 decimal places, and I can't believe it's this hard to accomplish!
Any help would be very gratefully received.
You are printing a number not a string
Xcode 11.4 • Swift 5.2 or later
extension Formatter {
static let usCurrency: NumberFormatter = {
let formatter = NumberFormatter()
formatter.locale = .init(identifier: "en_US")
formatter.numberStyle = .currency
return formatter
}()
}
extension String {
var double: Double? { Double(self) }
var usCurrencyFormatted: String {
Formatter.usCurrency.string(for: double) ?? Formatter.usCurrency.string(for: 0) ?? ""
}
}
"1.1222".usCurrencyFormatted // "$1.12"
"2".usCurrencyFormatted // "$2.00"
The problem is about numberFromString returning an optional - so you have to unwrap before printing. Just to be safe, you can use optional binding:
if let returnNumber = n.numberFromString(testnumber) {
println("Returned number is \(returnNumber)")
}
otherwise if it's ok for the app to crash if the optional is nil (in some cases this is a wanted behavior if the optional is expected to always contain a non nil value) just use forced unwrapping:
let returnNumber = n.numberFromString(testnumber)!
println("Returned number is \(returnNumber)")
That fixes the unwanted "Optional(xx)" text. As for formatting a float/double number, there are probably several ways of doing it - the one I would use is c-like string formatting, available via NSString:
let formattedNumber = NSString(format: "%.2f", returnNumber)
println("Returned number is \(formattedNumber)")
Use String Format Specifiers as reference if you want to know more about format specifiers.
You could probably just use the NSNumberFormatter that you just created.
let returnNumber = n.stringFromNumber(n.numberFromString(testnumber))
returnNumber will now be of type String.
The following returns to 2 decimal places for me in playgrounds. May be of some help to you. Uses NSNumberFormatter and then unwraps the optional
let testnumber: String = "1.50000"
let numberFormatter = NSNumberFormatter()
let number = numberFormatter.numberFromString(testnumber)
if let final = number?.floatValue {
println("Returned number is " + String(format: "%.2f", final))
}