How to find index of list item in Swift

Question

I am trying to find an item index by searching a list  Does anybody know how to do that    I see there is list StartIndex and list EndIndex but I want something like python s list index  text

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Update for Swift 2      sequence contains element   Returns true if a given sequence  such as   an array  contains the specified element    Swift 1   If you re looking just to check if an element is contained inside an array  that is  just get a boolean indicator  use contains sequence  element  instead of find array  element        contains sequence  element   Returns true if a given sequence  such as   an array  contains the specified element    See example below    var languages     Swift    Objective-C   contains languages   Swift      true contains languages   Java      false contains  29  85  42  96  75   42     true if  contains languages   Swift           Use contains in these cases  instead of find

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In Swift 4  if you are traversing through your DataModel array  make sure your data model conforms to Equatable Protocol   implement the lhs rhs method   and only then you can use   index of    For example  class Photo   Equatable      var imageURL  URL      init imageURL  URL           self imageURL   imageURL            static func     lhs  Photo  rhs  Photo  - gt  Bool          return lhs imageURL    rhs imageURL           And then   let index   self photos index of  aPhoto

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Any of this solution works for me  This the solution i have for Swift 4     let monday   Day name   M   let tuesday   Day name   T   let friday   Day name   F    let days    monday  tuesday  friday   let index   days index where                   important to test with     to be sure it s the same object reference              0     tuesday

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Just use firstIndex method       array firstIndex where     0    searchedItem

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While indexOf   works perfectly  it only returns one index   I was looking for an elegant way to get an array of indexes for elements which satisfy some condition   Here is how it can be done   Swift 3   let array     apple    dog    log    let indexes   array enumerated   filter        0 element contains  og         map  0 offset   print indexes    Swift 2   let array     apple    dog    log    let indexes   array enumerate   filter        0 element containsString  og         map  0 index   print indexes

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SWIFT 4  Let s say you want to store a number from the array called cardButtons into cardNumber  you can do it this way   let cardNumber   cardButtons index of  sender    sender is the name of your button

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Swift 4  For reference types   extension Array where Array Element  AnyObject        func index ofElement element  Element  - gt  Int            for  currentIndex  currentElement  in self enumerated                 if currentElement     element                   return currentIndex                                 return nil

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You can filter an array with a closure   var myList    1  2  3  4  var filtered   myList filter    0    3        lt   returns  3    And you can count an array   filtered count     lt   returns 1   So you can determine if an array includes your element by combining these   myList filter    0    3   count  gt  0      lt   returns true if the array includes 3   If you want to find the position  I don t see fancy way  but you can certainly do it like this   var found  Int       lt   will hold the index if it was found  or else will be nil for i in  0  x count        if x i     3           found   i           EDIT  While we re at it  for a fun exercise let s extend Array to have a find method   extension Array       func find includedElement  T - gt  Bool  - gt  Int            for  idx  element  in enumerate self                if includedElement element                    return idx                                 return nil           Now we can do this   myList find    0    3      returns the index position of 3 or nil if not found

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You can also use the functional library Dollar to do an indexOf on an array as such http   www dollarswift org  indexof-indexof    indexOf  1  2  3  1  2  3   value  2     gt  1

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In Swift 2  with Xcode 7   Array includes an indexOf method provided by the CollectionType protocol   Actually  two indexOf methods   one that uses equality to match an argument  and another that uses a closure    Prior to Swift 2  there wasn t a way for generic types like collections to provide methods for the concrete types derived from them  like arrays   So  in Swift 1 x   index of  is a global function    And it got renamed  too  so in Swift 1 x  that global function is called find   It s also possible  but not necessary  to use the indexOfObject method from NSArray    or any of the other  more sophisticated search meth dis from Foundation that don t have equivalents in the Swift standard library  Just import Foundation  or another module that transitively imports Foundation   cast your Array to NSArray  and you can use the many search methods on NSArray

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For SWIFT 3 you can use a simple function  func find objecToFind  String   - gt  Int       for i in 0   arrayName count         if arrayName i     objectToFind            return i              return nil     This will give the number position  so you can use like  arrayName remove at   find objecToFind       Hope to be useful

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Swift 4  If your array contains elements of type  String  AnyObject   So to find the index of element use the below code   var array     String  AnyObject       Save your data in array let objectAtZero   array 0     get first object let index    self array as NSArray  index of  objectAtZero    Or If you want to found index on the basis of key from Dictionary  Here array contains Objects of Model class and I am matching id property      let userId   20     if let index   array index where     dict  - gt  Bool in            return dict id    userId    Will found index of matched id              print  Index found         OR       let storeId   Int surveyCurrent store id     Accessing model key value       indexArrUpTo   self arrEarnUpTo index   Int  0 store id     storeId       Array contains models and finding specific one

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Swift 5  func firstIndex of element  Element  - gt  Int   var alphabets     A    B    E    D     Example1  let index   alphabets firstIndex where    0     A      Example2  if let i   alphabets firstIndex of   E         alphabets i     C     i is the index   print alphabets     Prints    A    B    C    D

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in Swift 4 2    index where   was changed to  firstIndex where    array firstIndex where    0     person1

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As swift is in some regards more functional than object-oriented  and Arrays are structs  not objects   use the function  find  to operate on the array  which returns an optional value  so be prepared to handle a nil value   let arr Array     a   b   c   find arr   c                    2 find arr   d                    nil   Update for Swift 2 0   The old find function is not supported any more with Swift 2 0   With Swift 2 0  Array gains the ability to find the index of an element using a function defined in an extension of CollectionType  which Array implements    let arr     a   b   c    let indexOfA   arr indexOf  a      0 let indexOfB   arr indexOf  b      1 let indexOfD   arr indexOf  d      nil   Additionally  finding the first element in an array fulfilling a predicate is supported by another extension of CollectionType   let arr2    1 2 3 4 5 6 7 8 9 10  let indexOfFirstGreaterThanFive   arr2 indexOf   0  gt  5      5 let indexOfFirstGreaterThanOneHundred   arr2 indexOf   0  gt  100      nil   Note that these two functions return optional values  as find did before   Update for Swift 3 0   Note the syntax of indexOf has changed  For items conforming to Equatable you can use   let indexOfA   arr index of   a     A detailed documentation of the method can be found at https   developer apple com reference swift array 1689674-index  For array items that don t conform to Equatable you ll need to use index where     let index   cells index where     item  - gt  Bool in   item foo    42    test if this is the item you re looking for      Update for Swift 4 2   With Swift 4 2  index is no longer used but is separated into firstIndex and lastIndex for better clarification  So depending on whether you are looking for the first or last index of the item   let arr     a   b   c   a    let indexOfA   arr firstIndex of   a      0 let indexOfB   arr lastIndex of   a      3

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tl dr   For classes  you might be looking for   let index   someArray firstIndex  0     someObject      Full answer   I think it s worth mentioning that with reference types  class  you might want to perform an identity comparison  in which case you just need to use the     identity operator in the predicate closure       Swift 5  Swift 4 2   let person1   Person name   John   let person2   Person name   Sue   let person3   Person name   Maria   let person4   Person name   Loner    let people    person1  person2  person3   let indexOfPerson1   people firstIndex  0     person1     0 let indexOfPerson2   people firstIndex  0     person2     1 let indexOfPerson3   people firstIndex  0     person3     2 let indexOfPerson4   people firstIndex  0     person4     nil   Note that the above syntax uses trailing closures syntax  and is equivalent to   let indexOfPerson1   people firstIndex where    0     person1      Swift 4   Swift 3 - the function used to be called index  Swift 2 - the function used to be called indexOf     Note the relevant and useful comment by paulbailey about class types that implement Equatable  where you need to consider whether you should be comparing using      identity operator  or     equality operator   If you decide to match using     then you can simply use the method suggested by others  people firstIndex of  person1

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Swift 2 1   var array     0   1   2   3    if let index   array indexOf  1        array removeAtIndex index     print array       0   2   3     Swift 3  var array     0   1   2   3    if let index   array index of   1         array remove at  index    array remove at  1

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For   gt   swift 4 0   It s rather very simple  Consider the following Array object   var names   String      jack    rose    jill     In order to obtain the index of the element rose  all you have to do is   names index of   rose      returns 1   Note    Array index of   returns an Optional lt Int gt    nil implies that the element isn t present in the array  You might want to force-unwrap the returned value or use an if-let to get around the optional

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If you are still working in Swift 1 x  then try   let testArray     A   B   C    let indexOfA   find testArray   A    let indexOfB   find testArray   B   let indexOfC   find testArray   C

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In case somebody has this problem  Cannot invoke initializer for type  Int  with an argument list of type   Array lt Element gt  Index      jsut do this  extension Int       var toInt  Int           return self           then  guard let finalIndex   index  toInt else       return false

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In Swift 4 5  use  firstIndex  for find index   let index   array firstIndex  0    value

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For custom class  you need to implement the Equatable protocol   import Foundation  func    l  MyClass  r  MyClass  - gt  Bool     return l id    r id    class MyClass  Equtable       init id  String            self msgID   id            let msgID  String    let item   MyClass 3  let itemList    MyClass 1   MyClass 2   item  let idx   itemList indexOf item   printl idx

[arrays] How to find index of list item in Swift?

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