How to create range in Swift

Question

In Objective-c we create range by using NSRange  NSRange range    So how to create range in Swift

User · Answer

You can use like this  let nsRange   NSRange location  someInt  length  someInt    as in  let myNSString   bigTOTPCode as NSString   12345678 let firstDigit   myNSString substringWithRange NSRange location  0  length  1     1 let secondDigit   myNSString substringWithRange NSRange location  1  length  1     2 let thirdDigit   myNSString substringWithRange NSRange location  2  length  4     3456

User · Answer

I want to do this    print  Hello  1   3      out  Error   But unfortunately  I can t write a subscript of my own because the loathed one takes up the name space    We can do this however    print  Hello  range  1   3      out  ell    Just add this to your project    extension String       subscript range  ClosedRange lt Int gt   - gt  String           get               let start   String Index utf16Offset  range lowerBound  in  self              let end   String Index utf16Offset  range upperBound  in  self              return String self start   end

User · Answer

1   lt 10    returns        Range   1   lt 10

User · Answer

I created the following extension   extension String       func substring from from Int  to Int  - gt  String            if from lt to  amp  amp  from gt  0  amp  amp  to lt self characters count               let rng   self startIndex advancedBy from    lt self startIndex advancedBy to              return self substringWithRange rng            else               return nil                     example of use   print  abcde  substring from  1  to  10     nil print  abcde  substring from  2  to  4      Optional  cd   print  abcde  substring from  1  to  0      nil print  abcde  substring from  1  to  1      nil print  abcde  substring from  -1  to  1     nil

User · Answer

I find it surprising that  even in Swift 4  there s still no simple native way to express a String range using Int  The only String methods that let you supply an Int as a way of obtaining a substring by range are prefix and suffix   It is useful to have on hand some conversion utilities  so that we can talk like NSRange when speaking to a String  Here s a utility that takes a location and length  just like NSRange  and returns a Range lt String Index gt    func range   start Int    length Int  - gt  Range lt String Index gt        let i   self index start  gt   0   self startIndex   self endIndex          offsetBy  start      let j   self index i  offsetBy  length      return i   lt j     For example   hello  range 0 1   is the Range lt String Index gt  embracing the first character of  hello   As a bonus  I ve allowed negative locations   hello  range -1 1   is the Range lt String Index gt  embracing the last character of  hello    It is useful also to convert a Range lt String Index gt  to an NSRange  for those moments when you have to talk to Cocoa  for example  in dealing with NSAttributedString attribute ranges   Swift 4 provides a native way to do that   let nsrange   NSRange range  in s     where s is the string   We can thus write another utility where we go directly from a String location and length to an NSRange   extension String       func nsRange   start Int    length Int  - gt  NSRange           return NSRange self range start length   in self

User · Answer

Xcode 8 beta 2      Swift 3  let myString    Hello World  let myRange   myString startIndex   lt myString index myString startIndex  offsetBy  5  let mySubString   myString substring with  myRange       Hello     Xcode 7     Swift 2 0  let myString    Hello World  let myRange   Range lt String Index gt  start  myString startIndex  end  myString startIndex advancedBy 5    let mySubString   myString substringWithRange myRange       Hello   or simply  let myString    Hello World  let myRange   myString startIndex   lt myString startIndex advancedBy 5  let mySubString   myString substringWithRange myRange       Hello

User · Answer

If anyone want to create NSRange object can create as   let range  NSRange   NSRange init location  0  length  5    this will create range with position 0 and length 5

User · Answer

func replace input  String  start  Int lenght  Int  newChar  Character  - gt  String       var chars   Array input characters       for i in start   lenght           guard i  lt  input characters count else              break                   chars i    newChar           return String chars

User · Answer

Use like this  var start   str startIndex    Start at the string s start index var end   advance str startIndex  5     Take start index and advance 5 characters forward var range  Range lt String Index gt    Range lt String Index gt  start  start end  end   let firstFiveDigit    str substringWithRange range   print firstFiveDigit    Output   Hello

User · Answer

Updated for Swift 4  Swift ranges are more complex than NSRange  and they didn t get any easier in Swift 3  If you want to try to understand the reasoning behind some of this complexity  read this and this  I ll just show you how to create them and when you might use them   Closed Ranges   a   b  This range operator creates a Swift range which includes both element a and element b  even if b is the maximum possible value for a type  like Int max   There are two different types of closed ranges  ClosedRange and CountableClosedRange   1  ClosedRange  The elements of all ranges in Swift are comparable  ie  they conform to the Comparable protocol   That allows you to access the elements in the range from a collection  Here is an example   let myRange  ClosedRange   1   3  let myArray     a    b    c    d    e   myArray myRange       b    c    d     However  a ClosedRange is not countable  ie  it does not conform to the Sequence protocol   That means you can t iterate over the elements with a for loop  For that you need the CountableClosedRange   2  CountableClosedRange  This is similar to the last one except now the range can also be iterated over   let myRange  CountableClosedRange   1   3  let myArray     a    b    c    d    e   myArray myRange       b    c    d    for index in myRange       print myArray index       Half-Open Ranges  a   lt b  This range operator includes element a but not element b  Like above  there are two different types of half-open ranges  Range and CountableRange   1  Range  As with ClosedRange  you can access the elements of a collection with a Range  Example   let myRange  Range   1   lt 3  let myArray     a    b    c    d    e   myArray myRange       b    c     Again  though  you cannot iterate over a Range because it is only comparable  not stridable    2  CountableRange  A CountableRange allows iteration    let myRange  CountableRange   1   lt 3  let myArray     a    b    c    d    e   myArray myRange       b    c    for index in myRange       print myArray index       NSRange  You can  must  still use NSRange at times in Swift  when making attributed strings  for example   so it is helpful to know how to make one   let myNSRange   NSRange location  3  length  2    Note that this is location and length  not start index and end index  The example here is similar in meaning to the Swift range 3   lt 5  However  since the types are different  they are not interchangeable   Ranges with Strings  The     and    lt  range operators are a shorthand way of creating ranges  For example   let myRange   1   lt 3   The long hand way to create the same range would be   let myRange   CountableRange lt Int gt  uncheckedBounds   lower  1  upper  3      1   lt 3   You can see that the index type here is Int  That doesn t work for String  though  because Strings are made of Characters and not all characters are the same size   Read this for more info   An emoji like   for example  takes more space than the letter  b    Problem with NSRange  Try experimenting with NSRange and an NSString with emoji and you ll see what I mean  Headache   let myNSRange   NSRange location  1  length  3   let myNSString  NSString    abcde  myNSString substring with  myNSRange      bcd   let myNSString2  NSString    acde  myNSString2 substring with  myNSRange      c     Where is the  d      The smiley face takes two UTF-16 code units to store  so it gives the unexpected result of not including the  d    Swift Solution  Because of this  with Swift Strings you use Range lt String Index gt   not Range lt Int gt   The String Index is calculated based on a particular string so that it knows if there are any emoji or extended grapheme clusters   Example  var myString    abcde  let start   myString index myString startIndex  offsetBy  1  let end   myString index myString startIndex  offsetBy  4  let myRange   start   lt end myString myRange      bcd   myString    acde  let start2   myString index myString startIndex  offsetBy  1  let end2   myString index myString startIndex  offsetBy  4  let myRange2   start2   lt end2 myString myRange2      cd    One-sided Ranges  a    and    b and    lt b  In Swift 4 things were simplified a bit  Whenever the starting or ending point of a range can be inferred  you can leave it off   Int  You can use one-sided integer ranges to iterate over collections  Here are some examples from the documentation      iterate from index 2 to the end of the array for name in names 2           print name        iterate from the beginning of the array to index 2 for name in names    2        print name        iterate from the beginning of the array up to but not including index 2 for name in names    lt 2        print name        the range from negative infinity to 5  You can t iterate forward    over this because the starting point in unknown  let range      5 range contains 7       false range contains 4       true range contains -1      true     You can iterate over this but it will be an infinate loop     so you have to break out at some point  let range   5      String  This also works with String ranges  If you are making a range with str startIndex or str endIndex at one end  you can leave it off  The compiler will infer it   Given  var str    Hello  playground  let index   str index str startIndex  offsetBy  5   let myRange      lt index       Hello   You can go from the index to str endIndex by using      var str    Hello  playground  let index   str index str endIndex  offsetBy  -10  let myRange   index              playground   See also    How does String Index work in Swift How does String substring work in Swift   Notes   You can t use a range you created with one string on a different string  As you can see  String ranges are a pain in Swift  but they do make it possibly to deal better with emoji and other Unicode scalars    Further Study   String Range examples Range Operator documentation Strings and Characters documentation

[swift] How to create range in Swift?

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