Converting String to Int with Swift

Question

The application basically calculates acceleration by inputting Initial and final velocity and time and then use a formula to calculate acceleration  However  since the values in the text boxes are string  I am unable to convert them to integers    IBOutlet var txtBox1   UITextField  IBOutlet var txtBox2   UITextField  IBOutlet var txtBox3   UITextField  IBOutlet var lblAnswer   UILabel    IBAction func btn1 sender   AnyObject         let answer1    The acceleration is      var answer2   txtBox1     var answer3   txtBox2     var answer4   txtBox3

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In Swift 4 2 and Xcode 10 1  let string String    789  let intValue Int   Int string   print intValue   let integerValue Int   789 let stringValue String   String integerValue        OR   let stringValue String      integerValue   print stringValue

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Basic Idea  note that this only works in Swift 1 x  check out ParaSara s answer to see how it works in Swift 2 x           toInt returns optional that s why we used a Int      let a Int    firstText text toInt      firstText is UITextField     let b Int    secondText text toInt      secondText is UITextField         check a and b before unwrapping using       if a  amp  amp  b           var ans   a    b          answerLabel text    Answer is   ans      answerLabel ie UILabel       else           answerLabel text    Input values are not numeric          Update for Swift 4      let a Int    Int firstText text     firstText is UITextField let b Int    Int secondText text     secondText is UITextField

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Xcode 8 1 and swift 3 0  We can also handle it by Optional Binding  Simply  let occur    10   if let occ   Int occur            print  By optional binding     occ 2     20

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swift 4 0  let stringNumber    123  let number   Int stringNumber    here number is of type  Int       using Forced Unwrapping  if number    nil               string is converted to Int     you could also use Optional Binding other than forced binding   eg     if let number   Int stringNumber           number is of type Int

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Useful for String to Int and other type  extension String             Converts String to Int         public func toInt   - gt  Int                if let num   NumberFormatter   number from  self                    return num intValue               else                   return nil                                    Converts String to Double         public func toDouble   - gt  Double                if let num   NumberFormatter   number from  self                    return num doubleValue               else                   return nil                                      EZSE  Converts String to Float         public func toFloat   - gt  Float                if let num   NumberFormatter   number from  self                    return num floatValue               else                   return nil                                    Converts String to Bool         public func toBool   - gt  Bool                return  self as NSString  boolValue                   Use it like      123  toInt      123

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Latest swift3 this code is simply to convert string to int  let myString    556  let myInt   Int myString

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An Int in Swift contains an initializer that accepts a String  It returns an optional Int  as the conversion can fail if the string contains not a number   By using an if let statement you can validate whether the conversion succeeded    So your code become something like this     IBOutlet var txtBox1   UITextField  IBOutlet var txtBox2   UITextField  IBOutlet var txtBox3   UITextField  IBOutlet var lblAnswer   UILabel   IBAction func btn1 sender   AnyObject         let answer1    The acceleration is      var answer2   txtBox1     var answer3   txtBox2     var answer4   txtBox3      if let intAnswer   Int txtBox1 text             Correctly converted

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Swift 3  The simplest and more secure way is    IBOutlet var textFieldA    UITextField  IBOutlet var textFieldB    UITextField  IBOutlet var answerLabel   UILabel   IBAction func calculate sender   AnyObject           if let intValueA   Int textFieldA               let intValueB   Int textFieldB                let result   intValueA   intValueB             answerLabel text    The acceleration is   result                 else                answerLabel text    The value   intValueA  and or   intValueB  are not a valid integer value                      Avoid invalid values setting keyboard type to number pad    textFieldA keyboardType    numberPad  textFieldB keyboardType    numberPad

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edit update  Xcode 11 4     Swift 5 2  Please check the comments through the code    IntegerField swift file contents   import UIKit  class IntegerField  UITextField           returns the textfield contents  removes non digit characters and converts the result to an integer value     var value  Int   string digits integer    0        var maxValue  Int   999 999 999     private var lastValue  Int   0      override func willMove toSuperview newSuperview  UIView                adds a target to the textfield to monitor when the text changes         addTarget self  action   selector editingChanged   for   editingChanged             sets the keyboard type to digits only         keyboardType    numberPad            set the text alignment to right         textAlignment    right            sends an editingChanged action to force the textfield to be updated         sendActions for   editingChanged               deletes the last digit of the text field     override func deleteBackward                note that the field text property default value is an empty string so force unwrap its value is safe            note also that collection remove at requires a non empty collection which is true as well in this case so no need to check if the collection is not empty          text  remove at  text  index before  text  endIndex              sends an editingChanged action to force the textfield to be updated         sendActions for   editingChanged             objc func editingChanged             guard value  lt   maxValue else               text   Formatter decimal string for  lastValue              return                      This will format the textfield respecting the user device locale and settings         text   Formatter decimal string for  value          print  Value    value          lastValue   value             You would need to add those extensions to your project as well     Extensions UITextField swift file contents   import UIKit extension UITextField       var string  String   text               Extensions Formatter swift file contents   import Foundation extension Formatter       static let decimal   NumberFormatter numberStyle   decimal        Extensions NumberFormatter swift file contents   import Foundation extension NumberFormatter       convenience init numberStyle  Style            self init           self numberStyle   numberStyle             Extensions StringProtocol swift file contents   extension StringProtocol where Self  RangeReplaceableCollection       var digits  Self   filter   isWholeNumber        var integer  Int    Int self          Sample project

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Swift5 float or int string to int   extension String       func convertStringToInt   - gt  Int           return Int Double self     0 0           let doubleStr    4 2     print 4 print doubleStr convertStringToInt     let intStr    4     print 4 print intStr convertStringToInt

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As of swift 3  I have to force my      string  amp  int with a     otherwise it just doesn t work   For example   let prefs   UserDefaults standard var counter  String  counter   prefs string forKey  counter   print  counter    counter       var counterInt   Int counter   counterInt   counterInt    1 print  counterInt    counterInt      OUTPUT  counter  1 counterInt  2

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You can use NSNumberFormatter   numberFromString yourNumberString   It s great because it returns an an optional that you can then test with if let to determine if the conversion was successful   eg    var myString      10   if let myNumber   NSNumberFormatter   numberFromString myString        var myInt   myNumber integerValue        do what you need to do with myInt   else          what ever error code you need to write     Swift 5  var myString      10   if let myNumber   NumberFormatter   number from  myString        var myInt   myNumber intValue        do what you need to do with myInt     else          what ever error code you need to write

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for Swift3 x  extension String       func toInt defaultValue  Int  - gt  Int           if let n   Int self trimmingCharacters in  CharacterSet whitespacesAndNewlines                 return n           else               return defaultValue

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myString toInt   -  convert the string value into int    Swift 3 x   If you have an integer hiding inside a string  you can convertby using the integer s constructor  like this   let myInt   Int textField text    As with other data types  Float and Double  you can also convert by using NSString   let myString    556  let myInt    myString as NSString  integerValue

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To convert user input  i e string  to int for calculation I did this   and it works        let num Int    Int firstTextField text         let sum Int   num -2      print sum

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Updated answer for Swift 2 0   toInt   method gives an error  as it was removed from String in Swift 2 x  Instead  the Int type now has an initializer that accepts a String  let a  Int    Int firstTextField text  let b  Int    Int secondTextField text

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Because a string might contain non-numerical characters you should use a guard to protect the operation  Example   guard let labelInt Int   Int labelString  else       return    useLabelInt

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This works for me     var a Int    Int userInput text

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My solution is to have a general extension for string to int conversion   extension String        default  it is a number suitable for your project if the string is not an integer      func toInt default  Int  - gt  Int           if let result   Int self                return result                   else               return default

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for Alternative solution  You can use extension a native type  You can test with playground    extension String       func add a  Int  - gt  Int            if let b   Int self                return b   a                   else               return nil                           2  add 1

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Swift 5 0 and Above  Working  In case if you are splitting the String it creates two substrings and not two Strings   This below method will check for Any and convert it t0 NSNumber its easy to convert a NSNumber to Int  Float what ever data type you need   Actual Code    Convert Any To Number Object Removing Optional Key Word  public func getNumber number  Any  - gt  NSNumber   guard let statusNumber NSNumber   number as  NSNumber  else       guard let statString String   number as  String else           guard let statSubStr   Substring   number as  Substring else               return 0                   if let myInteger   Int statSubStr                return NSNumber value myInteger                    else              return 0                      if let myInteger   Int statString            return NSNumber value myInteger            else if let myFloat   Float statString            return NSNumber value myFloat       else           return 0         return statusNumber     Usage  if let hourVal   getNumber number  hourStr  as  Int        Passing String to check and convert to Double  Double getNumber number   dict  OUT      0

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About int   and Swift 2 x  if you get a nil value after conversion check if you try to convert a string with a big number  for example  1073741824   in this case try   let bytesInternet   Int64   Int64 bytesInternetString

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I recently got the same issue  Below solution is work for me           let strValue    123          let result    strValue as NSString  integerValue

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i have made a simple program  where you have 2 txt field you take input form the user and add them to make it simpler to understand please find the code below     IBOutlet weak var result  UILabel   IBOutlet weak var one  UITextField   IBOutlet weak var two  UITextField    IBAction func add sender  AnyObject                let count   Int one text       let cal   Int two text       let sum   count    cal      result text    Sum is   sum       hope this helps

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Use this      get the values from text boxes     let a Double   firstText text bridgeToObjectiveC   doubleValue     let b Double   secondText text bridgeToObjectiveC   doubleValue      we checking against 0 0  because above function return 0 0 if it gets failed to convert     if  a    0 0   amp  amp   b    0 0            var ans   a   b         answerLabel text    Answer is   ans         else           answerLabel text    Input values are not numberic          OR  Make your UITextField KeyboardType as DecimalTab from your XIB or storyboard  and remove any if condition for doing any calculation  ie   var ans   a   b answerLabel text    Answer is   ans     Because keyboard type is DecimalPad there is no chance to enter other 0-9 or    Hope this help

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Question   string  4 0000  can not be convert into integer using Int  4 000     Answer   Int   check string is integer or not if yes then give you integer and otherwise nil  but Float or Double can convert any number string to respective Float or Double without giving nil  Example if you have  45  integer string but using Float  45   gives you 45 0 float value or using Double  4567   gives you 45 0   Solution   NSString string   45 000   integerValue or Int Float  45 000      to get correct result

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IBAction func calculateAclr   sender  Any        if let addition   addition arrayString   txtBox1 text  txtBox2 text  txtBox3 text           print  Answer     addition          lblAnswer text      addition            func addition arrayString   Any    - gt  Int         var answer Int      for arrayElement in arrayString           if let stringValue   arrayElement  let intValue   Int stringValue                 answer    answer    0    intValue                      return answer

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In Swift 4   extension String                   var numberValue NSNumber            let formatter   NumberFormatter           formatter numberStyle    decimal         return formatter number from  self          let someFloat    12  numberValue

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Swift 3 0  Try this  you don t need to check for any condition I have done everything just use this function  Send anything string  number  float  double  etc   you get a number as a value or 0 if it is unable to convert your value  Function   func getNumber number  Any   - gt  NSNumber       guard let statusNumber NSNumber   number as  NSNumber else               guard let statString String   number as  String else                       return 0                   if let myInteger   Int statString                        return NSNumber value myInteger                    else              return 0                     return statusNumber     Usage   Add the above function in code and to convert use let myNumber   getNumber number  myString   if the myString has a number or string it returns the number else it returns 0  Example 1   let number String    9834  print  printing number   getNumber number  number       Output  printing number 9834  Example 2   let number Double   9834 print  printing number   getNumber number  number       Output  printing number 9834  Example 3   let number   9834 print  printing number   getNumber number  number       Output  printing number 9834

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Convert String value to Integer in Swift 4  let strValue String    100  let intValue   strValue as  Int var intValueFromString Int   strValue as  Int or var intValueFromString   Int strValue

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