How do you use String substringWithRange or how do Ranges work in Swift

Question

I have not yet been able to figure out how to get a substring of a String in Swift   var str      Hello  playground    func test str  String  - gt  String    return str substringWithRange     What goes here         test  str    I m not able to create a Range in Swift  Autocomplete in the Playground isn   t super helpful - this is what it suggests   return str substringWithRange aRange  Range lt String Index gt     I haven t found anything in the Swift Standard Reference Library that helps  Here was another wild guess   return str substringWithRange Range 0  1     And this   let r Range lt String Index gt    Range lt String Index gt  start  0  end  2  return str substringWithRange r    I ve seen other answers  Finding index of character in Swift String  that seem to suggest that since String is a bridge type for NSString  the  old  methods should work  but it s not clear how - e g   this doesn t work either  doesn t appear to be valid syntax    let x   str substringWithRange NSMakeRange 0  3     Thoughts

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here is a example to get video-Id only  i e  6oL687G0Iso  from the whole URL in swift  let str    https   www youtube com watch v 6oL687G0Iso amp list PLKmzL8Ib1gsT-5LN3V2h2H14wyBZTyvVL amp index 2  var arrSaprate   str componentsSeparatedByString  v    let start   arrSaprate 1  let rangeOfID   Range start  start startIndex end start startIndex advancedBy 11   let substring   start rangeOfID  print substring

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For example to find the first name  up to the first space  in my full name   let name    Joris Kluivers   let start   name startIndex let end   find name        if end       let firstName   name start  end     else          no space found     start and end are of type String Index here and are used to create a Range lt String Index gt  and used in the subscript accessor  if a space is found at all in the original string    It s hard to create a String Index directly from an integer position as used in the opening post  This is because in my name each character would be of equal size in bytes  But characters using special accents in other languages could have used several more bytes  depending on the encoding used   So what byte should the integer refer to   It s possible to create a new String Index from an existing one using the methods succ and pred which will make sure the correct number of bytes are skipped to get to the next code point in the encoding  However in this case it s easier to search for the index of the first space in the string to find the end index

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Updated for Xcode 7  Adds String extension   Use   var chuck  String    Hello Chuck Norris  chuck 6   11       gt  Chuck   Implementation   extension String                 Subscript to allow for quick String substrings   Hello   0   1     He              subscript  r  Range lt Int gt   - gt  String           get               let start   self startIndex advancedBy r startIndex              let end   self startIndex advancedBy r endIndex - 1              return self substringWithRange start   lt end

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Simple extension for String   extension String        func substringToIndex index  Int  - gt  String           return self startIndex   startIndex advancedBy min index  characters count - 1

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In new Xcode 7 0 use      Playground - noun  a place where people can play  import UIKit  var name    How do you use String substringWithRange   let range   name startIndex advancedBy 0    lt name startIndex advancedBy 10  name substringWithRange range     OUT

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Swift 3 X    Xcode 8 X    Tested working easy solution   Use simple    let myString    12 12 2017 12 34 45  let newString   myString   myString  startIndex     lt  myString  index  myString  startIndex    offsetBy  10     print newString        Output   12 12 2017   For customization easily change   offsetBy  10    Change 10 to endIndex    When you change offsetBy  10 to 15 20 etc  Will cut your string    Thank you

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Swift 2  Simple  let str    My String  let subStr   str str startIndex advancedBy 3    str startIndex advancedBy 7      Strin    Swift 3  let startIndex   str index str startIndex  offsetBy  3  let endIndex   str index str startIndex  offsetBy  7   str startIndex   endIndex            Strin  str substring to  startIndex         My   str substring from  startIndex       String    Swift 4  substring to   and substring from   are deprecated in Swift 4   String str    lt startIndex          My   String str startIndex             String  String str startIndex   endIndex          Strin

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Well  I had the same issue and solved with the  bridgeToObjectiveC    function   var helloworld    Hello World   var world   helloworld bridgeToObjectiveC   substringWithRange NSMakeRange 6 6   println    world       should print World    Please note that in the example  substringWithRange in conjunction with NSMakeRange take the part of the string starting at index 6  character  W   and finishing at index 6   6 positions ahead  character       Cheers

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Swift 3 0  I decided to have a little fun with this and produce an extension on String  I might not be using the word truncate properly in what I m having the function actually do   extension String        func truncate from initialSpot  Int  withLengthOf endSpot  Int  - gt  String             guard endSpot  gt  initialSpot else   return nil           guard endSpot   initialSpot  lt   self characters count else   return nil            let truncated   String self characters dropFirst initialSpot           let lastIndex   truncated index truncated startIndex  offsetBy  endSpot           return truncated substring to  lastIndex            let favGameOfThronesSong    Light of the Seven   let word   favGameOfThronesSong truncate from  1  withLengthOf  4      ight

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There s been a lot of good examples of how to attack this problem  The original question was about using the substringWithRange  but as has been pointed out that s a harder way to go than just doing your own extension   The above range solution is good  You can also do this a dozen other ways  Here s yet another example of how you could do this   extension String      func sub start  Int  length  Int  - gt  String           assert start  gt   0   Cannot extract from a negative starting index           assert length  gt   0   Cannot extract a negative length string           assert start  lt   countElements self  - 1   cannot start beyond the end           assert start   length  lt   countElements self    substring goes past the end of the original           var a   self substringFromIndex start          var b   a substringToIndex length          return b         var s    apple12345  println s sub 6  length  4      prints  2345

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You can use the substringWithRange method  It takes a start and end String Index   var str    Hello  playground  str substringWithRange Range lt String Index gt  start  str startIndex  end  str endIndex      Hello  playground    To change the start and end index  use advancedBy n    var str    Hello  playground  str substringWithRange Range lt String Index gt  start  str startIndex advancedBy 2   end  str endIndex advancedBy -1       llo  playgroun    You can also still use the NSString method with NSRange  but you have to make sure you are using an NSString like this   let myNSString   str as NSString myNSString substringWithRange NSRange location  0  length  3     Note  as JanX2 mentioned  this second method is not safe with unicode strings

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The short answer is that this is really hard in Swift right now  My hunch is that there is still a bunch of work for Apple to do on convenience methods for things like this   String substringWithRange   is expecting a Range lt String Index gt  parameter  and as far as I can tell there isn t a generator method for the String Index type  You can get String Index values back from aString startIndex and aString endIndex and call  succ   or  pred   on them  but that s madness   How about an extension on the String class that takes good old Ints   extension String       subscript  r  Range lt Int gt   - gt  String           get               let subStart   advance self startIndex  r startIndex  self endIndex              let subEnd   advance subStart  r endIndex - r startIndex  self endIndex              return self substringWithRange Range start  subStart  end  subEnd                       func substring from  Int  - gt  String           let end   countElements self          return self from   lt end            func substring from  Int  length  Int  - gt  String           let end   from   length         return self from   lt end           let mobyDick    Call me Ishmael   println mobyDick 8   14                  Ishmael  let dogString    This  s name is Patch   println dogString 5   lt 6                     println dogString 5   5                    println dogString substring 5              s name is Patch  println dogString substring 5  length  1             Update  Swift beta 4 resolves the issues below   As it stands  in beta 3 and earlier   even Swift-native strings have some issues with handling Unicode characters  The dog icon above worked  but the following doesn t   let harderString    1 1    for character in harderString       println character      Output   1   1

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Rob Napier had already given a awesome answer using subscript  But i felt one drawback in that as there is no check for out of bound conditions  This can tend to crash  So i modified the extension and here it is  extension String       subscript  r  Range lt Int gt   - gt  String      Optional String as return value         get               let stringCount   self characters count as Int               Check for out of boundary condition             if  stringCount  lt  r endIndex      stringCount  lt  r startIndex                   return nil                           let startIndex   self startIndex advancedBy r startIndex               let endIndex   self startIndex advancedBy r endIndex - r startIndex               return self Range start  startIndex  end  endIndex                       Output below  var str2    Hello  World   var str3   str2 0   5    Hello  var str4   str2 0   lt 5    Hello var str5   str2 0   lt 15    nil   So i suggest always to check for the if let  if let string   str 0   5          Manipulate your string safely

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Since String is a bridge type for NSString  the  quot old quot  methods should work  but it s not clear how - e g   this doesn t work either  doesn t appear to be valid syntax    let x   str substringWithRange NSMakeRange 0  3     To me  that is the really interesting part of your question  String is bridged to NSString  so most NSString methods do work directly on a String  You can use them freely and without thinking  So  for example  this works just as you expect     delete all spaces from Swift String stateName stateName   stateName stringByReplacingOccurrencesOfString  quot   quot   withString  quot  quot    But  as so often happens   quot I got my mojo workin  but it just don t work on you  quot  You just happened to pick one of the rare cases where a parallel identically named Swift method exists  and in a case like that  the Swift method overshadows the Objective-C method  Thus  when you say str substringWithRange  Swift thinks you mean the Swift method rather than the NSString method     and then you are hosed  because the Swift method expects a Range lt String Index gt   and you don t know how to make one of those  The easy way out is to stop Swift from overshadowing like this  by casting explicitly  let x    str as NSString  substringWithRange NSMakeRange 0  3    Note that no significant extra work is involved here   quot Cast quot  does not mean  quot convert quot   the String is effectively an NSString  We are just telling Swift how to look at this variable for purposes of this one line of code  The really weird part of this whole thing is that the Swift method  which causes all this trouble  is undocumented  I have no idea where it is defined  it is not in the NSString header and it s not in the Swift header either

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SWIFT 2 0  simple   let myString    full text container  let substring   myString myString startIndex   lt myString startIndex advancedBy 3      prints  ful   SWIFT 3 0  let substring   myString myString startIndex   lt myString index myString startIndex  offsetBy  3      prints  ful   SWIFT 4 0  Substring operations return an instance of the Substring type  instead of String   let substring   myString myString startIndex   lt myString index myString startIndex  offsetBy  3      prints  ful     Convert the result to a String for long-term storage  let newString   String substring

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At the time I m writing  no extension is perfectly Swift 4 2 compatible  so here is one that covers all the needs I could think of   extension String       func substring from  Int   to  Int   - gt  String           if let start   from               guard start  lt  self count else                   return                                     if let end   to               guard end  gt   0 else                   return                                     if let start   from  let end   to               guard end - start  gt   0 else                   return                                     let startIndex  String Index         if let start   from  start  gt   0               startIndex   self index self startIndex  offsetBy  start            else               startIndex   self startIndex                    let endIndex  String Index         if let end   to  end  gt   0  end  lt  self count               endIndex   self index self startIndex  offsetBy  end   1            else               endIndex   self endIndex                    return String self startIndex    lt  endIndex              func substring from  Int  - gt  String           return self substring from  from  to  nil             func substring to  Int  - gt  String           return self substring from  nil  to  to             func substring from  Int   length  Int  - gt  String           guard length  gt  0 else               return                       let end  Int         if let start   from  start  gt  0               end   start   length - 1           else               end   length - 1                    return self substring from  from  to  end             func substring length  Int  to  Int   - gt  String           guard let end   to  end  gt  0  length  gt  0 else               return                       let start  Int         if let end   to  end - length  gt  0               start   end - length   1           else               start   0                    return self substring from  start  to  to            And then  you can use   let string    Hello World     string substring from  1  to  7 gets you  ello Wo  string substring to  7 gets you  Hello Wo  string substring from  3 gets you  lo World   string substring from  1  length  4 gets you  ello  string substring length  4  to  7 gets you  o Wo  Updated substring from  Int   length  Int  to support starting from zero

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You can use this extensions to improve substringWithRange  Swift 2 3  extension String          func substringWithRange start  Int  end  Int  - gt  String               if  start  lt  0    start  gt  self characters count                        print  start index   start  out of bounds               return                      else if end  lt  0    end  gt  self characters count                       print  end index   end  out of bounds               return                      let range   Range start  self startIndex advancedBy start   end  self startIndex advancedBy end           return self substringWithRange range             func substringWithRange start  Int  location  Int  - gt  String               if  start  lt  0    start  gt  self characters count                        print  start index   start  out of bounds               return                      else if location  lt  0    start   location  gt  self characters count                       print  end index   start   location  out of bounds               return                      let range   Range start  self startIndex advancedBy start   end  self startIndex advancedBy start   location           return self substringWithRange range            Swift 3  extension String       func substring start  Int  end  Int  - gt  String               if  start  lt  0    start  gt  self characters count                        print  start index   start  out of bounds               return                      else if end  lt  0    end  gt  self characters count                       print  end index   end  out of bounds               return                      let startIndex   self characters index self startIndex  offsetBy  start          let endIndex   self characters index self startIndex  offsetBy  end          let range   startIndex   lt endIndex          return self substring with  range             func substring start  Int  location  Int  - gt  String               if  start  lt  0    start  gt  self characters count                        print  start index   start  out of bounds               return                      else if location  lt  0    start   location  gt  self characters count                       print  end index   start   location  out of bounds               return                      let startIndex   self characters index self startIndex  offsetBy  start          let endIndex   self characters index self startIndex  offsetBy  start   location          let range   startIndex   lt endIndex          return self substring with  range            Usage   let str    Hello  playground   let substring1   str substringWithRange 0  end  5    Hello let substring2   str substringWithRange 7  location  10    playground

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let startIndex   text startIndex var range   startIndex advancedBy 1     lt  text endIndex advancedBy -4  let substring   text substringWithRange range    Full sample you can see here

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This works in my playground      String seq  Array str  2   4

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I tried to come up with something Pythonic   All the subscripts here are great  but the times I really need something simple is usually when I want to count from back  e g  string endIndex advancedBy -1   It supports nil values  for both start and end index  where nil would mean index at 0 for start  string characters count for end   extension String       var subString   Int   - gt   Int   - gt  String           return    start  in                end  in                 let startIndex   start    0  lt  0   self endIndex advancedBy start     self startIndex advancedBy start    0                  let endIndex   end    self characters count  lt  0   self endIndex advancedBy end     self startIndex advancedBy end    self characters count                   return startIndex  gt  endIndex        self substringWithRange startIndex    lt  endIndex                                   let dog    Dog   print dog subString nil  -1      Dog     EDIT  A more elegant solution   public extension String       struct Substring           var start  Int          var string  String          public subscript end  Int   - gt  String               let startIndex   start    0  lt  0   string endIndex advancedBy start     string startIndex advancedBy start    0              let endIndex   end    string characters count  lt  0   string endIndex advancedBy end     string startIndex advancedBy end    string characters count               return startIndex  gt  endIndex        string substringWithRange startIndex    lt  endIndex                       public subscript start  Int   - gt  Substring           return Substring start  start  string  self           let dog    Dog   print dog nil  -1      Dog

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You can use any of the substring methods in a Swift String extension I wrote https   bit ly JString   var string    hello  var sub   string substringFrom 3     or string 3   5  println sub     lo

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http   www learnswiftonline com reference-guides string-reference-guide-for-swift  shows that this works well   var str    abcd  str   str substringToIndex 1

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If you don t care about performance    this is probably the most concise solution in Swift 4  extension String       subscript range  CountableClosedRange lt Int gt   - gt  String           return enumerated   filter  0 offset  gt   range first   amp  amp   0 offset  lt  range last                reduce      0   String  1 element             It enables you to do something like this   let myStr    abcd  myStr 0   lt 2     produces  ab

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This is how you get a range from a string   var str    Hello  playground   let startIndex   advance str startIndex  1  let endIndex   advance startIndex  8  let range   startIndex   lt endIndex let substr   str range     ello  pl    The key point is that you are passing a range of values of type String Index  this is what advance returns  instead of integers    The reason why this is necessary  is that strings in Swift don t have random access  because of variable length of Unicode characters basically   You also can t do str 1   String Index is designed to work with their internal structure    You can create an extension with a subscript though  that does this for you  so you can just pass a range of integers  see e g  Rob Napier s answer

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It is much more simple than any of the answers here  once you find the right syntax   I want to take away the   and    let myString     ABCDEFGHI   let startIndex   advance myString startIndex  1    advance as much as you like let endIndex   advance myString endIndex  -1  let range   startIndex   lt endIndex let myNewString   myString substringWithRange  range     result will be  ABCDEFGHI  the startIndex and endIndex could also be used in   let mySubString   myString substringFromIndex startIndex    and so on   PS  As indicated in the remarks  there are some syntax changes in swift 2 which comes with xcode 7 and iOS9   Please look at this page

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Easy solution with little code   Make an extension that includes basic subStringing that nearly all other languages have   extension String       func subString start  Int  end  Int  - gt  String           let startIndex   self index self startIndex  offsetBy  start          let endIndex   self index startIndex  offsetBy  end           let finalString   self substring from  startIndex          return finalString substring to  endIndex            Simply call this with  someString subString start  0  end  6

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NOTE   airspeedswift makes some very insightful points on the trade-offs of this approach  particularly the hidden performance impacts  Strings are not simple beasts  and getting to a particular index may take O n  time  which means a loop that uses a subscript can be O n 2   You have been warned   You just need to add a new subscript function that takes a range and uses advancedBy   to walk to where you want   import Foundation  extension String       subscript  r  Range lt Int gt   - gt  String           get               let startIndex   self startIndex advancedBy r startIndex              let endIndex   startIndex advancedBy r endIndex - r startIndex               return self Range start  startIndex  end  endIndex                      var s    Hello  playground   println s 0   5         gt   Hello   println s 0   lt 5         gt   Hello     This should definitely be part of the language  Please dupe rdar   17158813   For fun  you can also add a   operator onto the indexes   func   lt T  ForwardIndex gt  var index  T  var count  Int  - gt  T     for    count  gt  0  --count        index   index succ         return index    s substringWithRange s startIndex 2    s startIndex 5     I don t know yet if this one should be part of the language or not

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Sample Code for how to get substring in Swift 2 0       i  Substring from starting index  Input -  var str    Swift is very powerful language   print str   str   str substringToIndex str startIndex advancedBy 5   print str    Output -  Swift is very powerful language  Swift    ii  Substring from particular index  Input -   var str    Swift is very powerful language   print str   str   str substringFromIndex str startIndex advancedBy 6   substringToIndex str startIndex advancedBy 2   print str    Output -  Swift is very powerful language  is   I hope it will help you

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In Swift3  For ex  a variable  Duke James Thomas   we need to get   James        let name    Duke James Thomas  let range  Range lt String Index gt    name range of  James    let lastrange  Range lt String Index gt    img range of  Thomas    var middlename   name range lowerBound   lt lstrange lowerBound  print  middlename

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First create the range  then the substring  You can use fromIndex   lt toIndex syntax like so   let range   fullString startIndex   lt fullString startIndex advancedBy 15     15 first characters of the string let substring   fullString substringWithRange range

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If you have an NSRange  bridging to NSString works seamlessly  For example  I was doing some work with UITextFieldDelegate and I quickly wanted to compute the new string value when it asked if it should replace the range    func textField textField  UITextField  shouldChangeCharactersInRange range  NSRange  replacementString string  String  - gt  Bool       let newString    textField text as NSString  stringByReplacingCharactersInRange range  withString  string      println  Got new string     newString

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try this in playground  var str String    Hello  playground   let range   Range start advance str startIndex 1   end  advance str startIndex 8     it will give you  ello  p   However where this gets really interesting is that if you make the last index bigger than the string in playground it will show any strings that you defined after str  o  Range   appears to be a generic function so that it needs to know the type it is dealing with   You also have to give it the actual string your interested in playgrounds as it seems to hold all stings in a sequence one after another with their variable name afterwards   So  var str String    Hello  playground   var str2 String    I m the next string   let range   Range start advance str startIndex 1   end  advance str startIndex 49     gives  ello  playground str   I m the next string str2    works even if str2 is defined with a let

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Taking a page from Rob Napier  I developed these Common String Extensions  two of which are   subscript  r  Range lt Int gt   - gt  String       get           let startIndex   advance self startIndex  r startIndex          let endIndex   advance self startIndex  r endIndex - 1           return self Range start  startIndex  end  endIndex            func subString startIndex  Int  length  Int  - gt  String       var start   advance self startIndex  startIndex      var end   advance self startIndex  startIndex   length      return self substringWithRange Range lt String Index gt  start  start  end  end       Usage    Awesome  3   7     some   Awesome  subString 3  length  4     some

[swift] How do you use String.substringWithRange? (or, how do Ranges work in Swift?)

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