Generating random numbers with Swift

Question

I need to generate a random number    It appears the arc4random function no longer exists as well as the arc4random uniform function    The options I have are arc4random stir      arc4random buf UnsafeMutablePointer lt Void gt   Int   and   arc4random addrandom UnsafeMutablePointer lt UInt8 gt   Int32     I can t find any docs on the functions and no comments in the header files give hints

User · Answer

let MAX   UInt32   9 let MIN   UInt32   1  func randomNumber        var random number   Int arc4random uniform MAX    MIN     print   random      random number

User · Answer

Don t forget that some numbers will repeat  so you need to do something like      my totalQuestions was 47   func getRandomNumbers totalQuestions Int  - gt  NSMutableArray        var arrayOfRandomQuestions   Int            print  arraySizeRequired   40       print  totalQuestions     totalQuestions           This will output a 40 random numbers between 0 and totalQuestions  47      while arrayOfRandomQuestions count  lt  40                let limit  UInt32   UInt32 totalQuestions           let theRandomNumber    Int arc4random uniform limit                 if arrayOfRandomQuestions contains theRandomNumber                                print  ping                              else                             item not found                 arrayOfRandomQuestions append theRandomNumber                            print  Random Number set     arrayOfRandomQuestions        print  arrayOutputCount     arrayOfRandomQuestions count          return arrayOfRandomQuestions as  NSMutableArray

User · Answer

look  i had the same problem but i insert  the function as a global variable  as   var RNumber   Int arc4random uniform 9  1   func GetCase     your code     obviously this is not efficent  so then i just copy and paste the code into the function so it could be reusable  then xcode suggest me to set the var as constant so my code were  func GetCase      let RNumber   Int arc4random uniform 9  1      if categoria    1             well thats a part of my code so xcode tell me something of inmutable and initialization but  it build the app anyway and that advice simply dissapear  hope it helps

User · Answer

In Swift 3     It will generate random number between 0 to limit  let limit   UInt32   6 print  Random Number     arc4random uniform limit

User · Answer

Another option is to use the xorshift128plus algorithm   func xorshift128plus seed0   UInt64    seed1   UInt64  - gt     - gt  UInt64       var state0   UInt64   seed0     var state1   UInt64   seed1     if state0    0  amp  amp  state1    0           state0   1    both state variables cannot be 0            func rand   - gt  UInt64           var s1   UInt64   state0         let s0   UInt64   state1         state0   s0         s1    s1  lt  lt  23         s1    s1  gt  gt  17         s1    s0         s1    s0  gt  gt  26         state1   s1         return UInt64 addWithOverflow state0  state1  0            return rand     This algorithm has a period of 2 128 - 1 and passes all the tests of the BigCrush test suite  Note that while this is a high-quality pseudo-random number generator with a long period  it is not a cryptographically secure random number generator   You could seed it from the current time or any other random source of entropy  For example  if you had a function called urand64   that read a UInt64 from  dev urandom  you could use it like this   let rand   xorshift128plus urand64    urand64    for   in 1   10       print rand

User · Answer

This is how I get a random number between 2 int s   func randomNumber MIN  Int  MAX  Int - gt  Int      var list    Int           for i in MIN   MAX           list append i            return list Int arc4random uniform UInt32 list count         usage   print  My Random Number is    randomNumber MIN -10 MAX 10

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My implementation as an Int extension  Will generate random numbers in range from   lt to  public extension Int       static func random from  Int  to  Int  - gt  Int           guard to  gt  from else               assertionFailure  Can not generate negative random numbers               return 0                   return Int arc4random uniform UInt32 to - from     UInt32 from

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Lets Code with Swift for the random number or random string     let quotes  NSArray     R    A    N    D    O    M          let randomNumber   arc4random uniform UInt32 quotes count         let quoteString   quotes Int randomNumber         print quoteString    it will give you output randomly

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Swift 4 2   Xcode 10        let randomIntFrom0To10   Int random in  1   lt 10  let randomFloat   Float random in  0   lt 1      if you want to get a random element in an array let greetings     hey    hi    hello    hola   greetings randomElement     Under the hood Swift uses arc4random buf to get job done          Swift 4 1   Xcode 9        arc4random   returns a random number in the range of 0 to 4  294  967  295  drand48   returns a random number in the range of 0 0 to 1 0  arc4random uniform N  returns a random number in the range of 0 to N - 1  Examples   arc4random        gt  UInt32   2739058784 arc4random        gt  UInt32   2672503239 arc4random        gt  UInt32   3990537167 arc4random        gt  UInt32   2516511476 arc4random        gt  UInt32   3959558840  drand48        gt  Double   0 88642843322303122 drand48        gt  Double   0 015582849408328769 drand48        gt  Double   0 58409022031727176 drand48        gt  Double   0 15936862653180484 drand48        gt  Double   0 38371587480719427  arc4random uniform 3       gt  UInt32   0 arc4random uniform 3       gt  UInt32   1 arc4random uniform 3       gt  UInt32   0 arc4random uniform 3       gt  UInt32   1 arc4random uniform 3       gt  UInt32   2   arc4random uniform   is recommended over constructions like arc4random     upper bound as it avoids  modulo bias  when the upper bound is not a power of two

User · Answer

I m late to the party   Using a function that allows you to change the size of the array and the range selection on the fly is the most versatile method  You can also use map so it s very concise  I use it in all of my performance testing bench marking   elements is the number of items in the array only including numbers from 0   max  func randArr   elements  Int    max  Int  - gt   Int            return  0   lt elements  map    in Int random in  0   max            Code Sense   Placeholders look like this  randArr elements  Int  max  Int   10 elements in my array ranging from 0 to 1000   randArr 10  1000      554  8  54  87  10  33  349  888  2  77

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you can use this in specific rate   let die    1  2  3  4  5  6   let firstRoll   die Int arc4random uniform UInt32 die count      let secondRoll   die Int arc4random uniform UInt32 die count

User · Answer

Just call this function and provide minimum and maximum range of number and you will get a random number   eg like randomNumber MIN  0  MAX  10  and  You will get number between 0 to 9   func randomNumber MIN  Int  MAX  Int - gt  Int      return Int arc4random uniform UInt32 MAX-MIN     UInt32 MIN        Note - You will always get output an Integer number

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Update with swift 4 2    let randomInt   Int random in  1   lt 5  let randomFloat   Float random in  1   lt 10  let randomDouble   Double random in  1   100  let randomCGFloat   CGFloat random in  1   1000

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After some investigation I wrote this   import Foundation  struct Math      private static var seeded   false     static func randomFractional   - gt  CGFloat          if  Math seeded            let time   Int NSDate   timeIntervalSinceReferenceDate           srand48 time           Math seeded   true                return CGFloat drand48             Now you can just do Math randomFraction   to get random numbers  0  1  without having to remember seeding first  Hope this helps someone  o

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Another option is to use GKMersenneTwisterRandomSource from GameKit  The docs say      A deterministic pseudo-random source that generates random numbers   based on a mersenne twister algorithm  This is a deterministic random   source suitable for creating reliable gameplay mechanics  It is   slightly slower than an Arc4 source  but more random  in that it has a   longer period until repeating sequences  While deterministic  this is   not a cryptographic random source  It is however suitable for   obfuscation of gameplay data    import GameKit  let minValue   0 let maxValue   100  var randomDistribution  GKRandomDistribution  let randomSource   GKMersenneTwisterRandomSource   randomDistribution   GKRandomDistribution randomSource  randomSource  lowestValue  minValue  highestValue  maxValue  let number   randomDistribution  nextInt      0 print number    Example taken from Apple s sample code  https   github com carekit-apple CareKit blob master CareKitPrototypingTool OCKPrototyper CareKitPatient RandomNumberGeneratorHelper swift

User · Answer

You could try as well   let diceRoll   Int arc4random uniform UInt32 6      I had to add  UInt32  to make it work

[swift] Generating random numbers with Swift

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