Convert String to Float in Swift

Question

I m trying to convert numbers taken from a UITextField  which I presume  are actually Strings  and convert them to Float  so I can multiply them   I have two UITextfields which are declared as follows    IBOutlet var wage  UITextField  IBOutlet var hour  UITextField   When the user presses a UIButton I want to calculate the wages the user earns  but I can t  as I need to convert them to floats first  before I can use them   I know how to convert them to an integer by doing this   var wageConversion Int   0 wageConversion   wage text toInt      However  I have no idea how to convert them to floats

User · Answer

Swift 4 5  use just Float value    let string value   String    123200   let float value   Float   Float string value   print float value    Answer  123200

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import Foundation  -23 67  floatValue      gt  -23 67  let s    -23 67  as NSString s floatValue      gt  -23 67

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to convert string to Float in Xcode 11 as previous methods need modification func stringToFloat value   String  - gt  Float       let numberFormatter   NumberFormatter       let number   numberFormatter number from  value      let numberFloatValue   number  floatValue     return numberFloatValue

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Double   builds an Double from an Int  like this   var convertedDouble   Double someInt   Note that this will only work if your text actually contains a number  Since Wage is a text field  the user can enter whatever they want and this will trigger a runtime error when you go to unbox the Optional returned from toInt    You should check that the conversion succeeded before forcing the unboxing   if let wageInt   Wage text  toInt           we made it in the if so the conversion succeeded      var wageConversionDouble   Double wageInt      Edit   If you re sure the text will be an integer  you can do something like this  note that text on UITextField is also Optional     if let wageText   Wage text       var wageFloat   Double wageText toInt

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Using the accepted solution  I was finding that my  1 1   when using the  floatValue conversion  would get converted to 1 10000002384186  which was not what I wanted   However  if I used the  doubleValue instead  I would get the 1 1 that I wanted   So for example  instead of using the accepted solution  I used this instead   var WageConversion    Wage text as NSString  doubleValue   In my case I did not need double-precision  but using the  floatValue was not giving me the proper result     Just wanted to add this to the discussion in case someone else had been running into the same issue

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Swift 2 0    Now with Swift 2 0 you can just use Float Wage text  which returns a Float  type  More clear than the below solution which just returns 0   If you want a 0 value for an invalid Float for some reason you can use Float Wage text     0 which will return 0 if it is not a valid Float     Old Solution  The best way to handle this is direct casting   var WageConversion    Wage text as NSString  floatValue   I actually created an extension to better use this too   extension String       var floatValue  Float           return  self as NSString  floatValue           Now you can just call var WageConversion   Wage text floatValue and allow the extension to handle the bridge for you   This is a good implementation since it can handle actual floats  input with    and will also help prevent the user from copying text into your input field  12p 34  or even 12 12 41    Obviously  if Apple does add a floatValue to Swift this will throw an exception  but it may be nice in the mean time  If they do add it later  then all you need to do to modify your code is remove the extension and everything will work seamlessly  since you will already be calling  floatValue   Also  variables and constants should start with a lower case  including IBOutlets

User · Answer

I convert String to Float in this way   let numberFormatter   NSNumberFormatter   let number   numberFormatter numberFromString  15 5   let numberFloatValue   number floatValue  println  number is   numberFloatValue       prints  number is 15 5

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This is how I approached it  I did not want to  cross the bridge   as it has been removed from Xcode 6 beta 5 anyway  quick and dirty   extension String           converting a string to double     func toDouble   - gt  Double                split the string into components         var comps   self componentsSeparatedByString                  we have nothing         if comps count    0               return nil                      if there is more than one decimal         else if comps count  gt  2               return nil                   else if comps 0           comps 1                      return nil                       grab the whole portion         var whole   0 0            ensure we have a number for the whole         if let w   comps 0  toInt                 whole   Double w                    else               return nil                       we only got the whole         if comps count    1                return whole                        grab the fractional         var fractional   0 0            ensure we have a number for the fractional         if let f   comps 1  toInt                     use number of digits to get the power             var toThePower   Double countElements comps 1                    compute the fractional portion             fractional   Double f    pow 10 0  toThePower                     else               return nil                       return the result         return whole   fractional               converting a string to float     func toFloat   - gt  Float             if let val   self toDouble                 return Float val                    else               return nil                          test it out var str    78 001   if let val   str toFloat         println  Str in float    val      else       println  Unable to convert Str to float         now in double if let val   str toDouble         println  Str in double    val      else       println  Unable to convert Str to double

User · Answer

you can use   let wg   Float wage text     If you want to round the float to 2 decimal places   let wg   Float String format     2f  wage text

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Below will give you an optional Float  stick a   at the end if you know it to be a Float  or use if let    let wageConversion   Float wage text

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Because in some parts of the world  for example  a comma is used instead of a decimal   It is best to create a NSNumberFormatter to convert a string to float   let numberFormatter   NSNumberFormatter   numberFormatter numberStyle   NSNumberFormatterStyle DecimalStyle let number   numberFormatter numberFromString self stringByTrimmingCharactersInSet Wage text

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extension String           func floatValue   - gt  Float            return Float self

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For the sake of completeness this is a solution using an extension of UITextField which can also consider a different locale   For Swift 3   extension UITextField       func floatValue locale   Locale   Locale current  - gt  Float           let numberFormatter   NumberFormatter           numberFormatter numberStyle    decimal         numberFormatter locale   locale          let nsNumber   numberFormatter number from  text           return nsNumber    nil   0 0   nsNumber  floatValue

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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

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Here is a Swift 3 adaptation of Paul Hegarty s solution from rdprado s answer  with some checking for optionals added to it  returning 0 0 if any part of the process fails    var wageFloat Float   0 0  if let wageText   wage text       if let wageNumber   NumberFormatter   number from  wageText            wageFloat   wageNumber floatValue           By the way  I took Stanford s CS193p class using iTunes University when it was still teaching Objective-C    I found Paul Hegarty to be a FANTASTIC instructor  and I would highly recommend the class to anyone starting out as an iOS developer in Swift

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Easy way      toInt returns optional that s why we used a Int  let a Int    firstText text toInt   let b Int    secondText text toInt       check a and b before unwrapping using   if a  amp  amp  b       var ans   a    b      answerLabel text    Answer is   ans     else       answerLabel text    Input values are not numberic      you can use same approach for other calculations  hope this help

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Update  The accepted answer shows a more up to date way of doing  Swift 1  This is how Paul Hegarty has shown on Stanford s CS193p class in 2015   wageConversion   NSNumberFormatter   numberFromString wage text    floatValue   You can even create a computed property for not having to do that every time  var wageValue  Float           get               return NSNumberFormatter   numberFromString wage text    floatValue                   set               wage text      newValue

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In swift 4  let Totalname    10 0    Now it is in string  let floatVal     Totalname as NSString  floatValue   Now converted to float

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You have two options which are quite similar  by the approach and result       option 1  var string 1   String    100  var double 1   Double    string 1 as NSString  doubleValue   99 0     option 2   var string 2   NSString    100     or   var string 2    100  as NSString var number 2   Double   string 2 doubleValue

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I found another way to take a input value of a UITextField and cast it to a float       var tempString String      var myFloat Float        IBAction func ButtonWasClicked   sender  Any           tempString   myUITextField text        myFloat   Float tempString

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Works on Swift 5   import Foundation  let myString String    quot 50 quot  let temp   myString as NSString let myFloat   temp floatValue print myFloat     50 0 print type of  myFloat      Float     Also you can guard your value in order to check what is happening whenever your app crashes  guard let myFloat   temp floatValue else   fatalError  quot  fail to change string to float value  quot

[string] Convert String to Float in Swift

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