Swift - Extract Double value from String [closed] - string

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How do I check if my string only contains [0-9] and .?
I’d like all other symbols to be deleted from my string.
If a user inputs any String
var anyString:String = “3f00b6r.beAwes0me4me”
I want to extract all the numbers from it (including one . if present) and remove all the other characters.
var myDouble:Double = 3006.04
Someone who know how to do that ?

Answer 1

You can use NSRegularExpression, like this:
// First set up error for checking
var error:NSError?
// Create regular expression pattern to search for numbers one digit in length or longer
let regexString = NSRegularExpression(pattern: "[0-9]{1,}.[0-9]{1,}|[0-9]{1,}", options: nil, error: &error)
// example string
let string = "find the number 10.19"
// get the string length
let strLength = count(string)
// To return the result first of all obtain the range of the first match if there is one, if let used here because NSRegularExpression returns an optional (we could of checked earlier, but I didn't)
if let rangeOfFirstMatch = regexString?.rangeOfFirstMatchInString(string, options: nil, range: NSMakeRange(0, strLength))
{
// if a range has been found that isn't equal to NSNotFound then build a range for the found string
if !NSEqualRanges(rangeOfFirstMatch, NSMakeRange(NSNotFound, 0)) {
advance(string.startIndex, rangeOfFirstMatch.length)
let r = Range(start: advance(string.startIndex, rangeOfFirstMatch.location), end: advance(string.startIndex, rangeOfFirstMatch.location+rangeOfFirstMatch.length))
// return the value
let substringForFirstMatch = string.substringWithRange(r)
println("Here's your match: \(substringForFirstMatch)")
}
}
There's also String.stringByTrimmingCharactersInSet() which would be cleaner and quicker but isn't as versatile. For instance the above string would also be returned if you did this:
let set = NSMutableCharacterSet.alphanumericCharacterSet()
set.addCharactersInString(" ")
set.removeCharactersInString("0123456789.")
string.stringByTrimmingCharactersInSet(set)
But if the string changed to "find the number ??...10.19...." then the stringByTrimmingCharactersInSet() would let you down and return "??...10.19...." while the regular expression version would hold up.
To make things easier a String extension could be written like this for returning multiple numbers in a string of type Double or Int:
extension String {
func stringsMatchingRegularExpression(expression exp:String, error err:NSErrorPointer) -> [String]? {
var strArray:[String]?
var rangeArray:[NSRange]?
let strLength = count(self)
var startOfRange = 0
if let regexString = NSRegularExpression(pattern: exp, options: nil, error: err) {
while startOfRange <= strLength {
let rangeOfMatch = regexString.rangeOfFirstMatchInString(self, options: nil, range: NSMakeRange(startOfRange, strLength-startOfRange))
if let rArray = rangeArray {
rangeArray = rArray + [rangeOfMatch]
}
else {
rangeArray = [rangeOfMatch]
}
startOfRange = rangeOfMatch.location+rangeOfMatch.length
}
if let ranArr = rangeArray {
for r in ranArr {
if !NSEqualRanges(r, NSMakeRange(NSNotFound, 0)) {
advance(self.startIndex, r.length)
let r = Range(start: advance(self.startIndex, r.location), end: advance(string.startIndex, r.location+r.length))
// return the value
let substringForMatch = self.substringWithRange(r)
if let sArray = strArray {
strArray = sArray + [substringForMatch]
}
else {
strArray = [substringForMatch]
}
}
}
}
}
return strArray
}
}
let myString = "one number is 7.5, another is 20"
let subStringArray = myString.stringsMatchingRegularExpression(expression: "[0-9]{1,}.[0-9]{1,}|[0-9]{1,}", error: nil)
subStringArray?[0] // 7.5
subStringArray?[1] // 20
Swift 2.0 Update for Extension
extension String {
func stringsMatchingRegularExpression(expression exp:String) -> [String]? {
var strArray:[String]?
var rangeArray:[NSRange]?
let strLength = self.characters.count
var startOfRange = 0
do {
let regexString = try NSRegularExpression(pattern: exp, options: [])
while startOfRange <= strLength {
let rangeOfMatch = regexString.rangeOfFirstMatchInString(self, options: [], range: NSMakeRange(startOfRange, strLength-startOfRange))
if let rArray = rangeArray {
rangeArray = rArray + [rangeOfMatch]
}
else {
rangeArray = [rangeOfMatch]
}
startOfRange = rangeOfMatch.location+rangeOfMatch.length
}
if let ranArr = rangeArray {
for r in ranArr {
if !NSEqualRanges(r, NSMakeRange(NSNotFound, 0)) {
self.startIndex.advancedBy(r.length)
let r = Range(start: self.startIndex.advancedBy(r.location), end: self.startIndex.advancedBy(r.location + r.length))
// return the value
let substringForMatch = self.substringWithRange(r)
if let sArray = strArray {
strArray = sArray + [substringForMatch]
}
else {
strArray = [substringForMatch]
}
}
}
}
} catch {
}
return strArray
}
}
let myString = "one number is 7.5, another is 20"
let subStringArray = myString.stringsMatchingRegularExpression(expression: "[-+]?\\d+.?\\d+")
subStringArray?[0] // 7.5
subStringArray?[1] // 20
Swift 3.0 Update for Extension
extension String {
func stringsMatchingRegularExpression(expression exp:String) -> [String]? {
var strArray:[String]?
var rangeArray:[NSRange]?
let strLength = self.characters.count
var startOfRange = 0
do {
let regexString = try NSRegularExpression(pattern: exp, options: [])
while startOfRange <= strLength {
let rangeOfMatch = regexString.rangeOfFirstMatch(in: self, options: [], range: NSMakeRange(startOfRange, strLength-startOfRange))
if let rArray = rangeArray {
rangeArray = rArray + [rangeOfMatch]
}
else {
rangeArray = [rangeOfMatch]
}
startOfRange = rangeOfMatch.location+rangeOfMatch.length
}
if let ranArr = rangeArray {
for r in ranArr {
if !NSEqualRanges(r, NSMakeRange(NSNotFound, 0)) {
self.index(startIndex, offsetBy: r.length)
let r = self.index(startIndex, offsetBy:r.location)..<self.index(startIndex, offsetBy:r.location + r.length)
// return the value
let substringForMatch = self.substring(with: r)
if let sArray = strArray {
strArray = sArray + [substringForMatch]
}
else {
strArray = [substringForMatch]
}
}
}
}
}
catch {
// catch errors here
}
return strArray
}
}
let myString = "one number is 7.5, another is 20"
let subStringArray = myString.stringsMatchingRegularExpression(expression: "[-+]?\\d+.?\\d+")
subStringArray?[0] // 7.5
subStringArray?[1] // 20