How does one make random number between range for arc4random uniform

Question

so my goal in this codebit is to randomly roll two dice and as we all know your regular die only has 6 sides so I imported Foundation for access to arc4random uniform UInt32   I attempted using the range of  1  7  to avoid randomly getting 0 however that returned an error which I didn t enjoy too much  I tried to do this   dice1   arc4random uniform UInt32 1  7     however that returned     Could not find an overload for  init  that accepts the supplied arguments   I hope that this is enough information for you amazing debs out there to help me     Please note I am just doing this in a playground to practice swift  It isn t imperative that I learn how to do this  it s just me tinkering before I jump into building actual apps  D    imports random number function import Foundation   creates data storage for dice roll var dice1  UInt32   0 var dice2  UInt32   0   counter variable var i   0   how many times snake eyes happens var snakeeyes   0    how many times a double is rolled var  double    0   rolls dice 100 times while i  lt  100        from here       sets dice roll   This returns an error of  Range  T3  is not convertible to UInt32      dice1   arc4random uniform 1  7     dice2   arc4random uniform 1  7           checks for snake eyes     if dice1    1  amp  amp  dice2    1           snakeeyes   snakeeyes   1              checks for doubles     if dice1    dice2           double     double    1             increases counter         i   i   1       to here   println  You got Snake Eyes   snakeeyes  times    println  You got Doubles     double   times

User · Accepted Answer

I believe you should do   dice1   arc4random uniform 6    1    to get the range 1 - 6  I don t do iOS objective C nor have I any knowledge on swift-language though  The random method should return a value between 0 and 5  and   1 will make it a value between 1 and 6   If you need a range between lets say 10 - 30 then just do   int random   arc4random uniform 21    10

User · Answer

I ve made an Int type extension  tested it in playground  hope this is useful  It also accepts negative ranges   extension Int       static func random range  Range lt Int gt    - gt  Int               var offset   0          if range startIndex  lt  0      allow negative ranges                       offset   abs range startIndex                     let mini   UInt32 range startIndex   offset          let maxi   UInt32 range endIndex     offset           return Int mini   arc4random uniform maxi - mini   - offset           use like  var aRandomInt   Int random -500   100      returns a random number within the given range    or define it as a Range extension as property like this   extension Range       var randomInt  Int               get                       var offset   0              if  startIndex as Int   lt  0      allow negative ranges                               offset   abs startIndex as Int                             let mini   UInt32 startIndex as Int   offset              let maxi   UInt32 endIndex   as Int   offset               return Int mini   arc4random uniform maxi - mini   - offset                       usage example  get an Int within the given Range  let nr    -1000     1100  randomInt

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Swift 3 Xcode Beta 5 Solution   Based on Ted van Gaalen Answer   extension Int          static func random range  Range lt Int gt    - gt  Int               var offset   0          if range lowerBound  lt  0      allow negative ranges                       offset   Swift abs range lowerBound                     let mini   UInt32 range lowerBound   offset          let maxi   UInt32 range upperBound     offset           return Int mini   arc4random uniform maxi - mini   - offset

User · Answer

That s because arc4random uniform   is defined as follows   func arc4random uniform    UInt32  - gt  UInt32   It takes a UInt32 as input  and spits out a UInt32  You re attempting to pass it a range of values  arc4random uniform gives you a random number in between 0 and and the number you pass it  exclusively   so if for example  you wanted to find a random number between -50 and 50  as in  -50  50  you could use arc4random uniform 101  - 50

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Probably one find useful this a bit updated version of Range extension from Ted van Gaalen s answer using Swift 4 Xcode 9    extension CountableClosedRange where Bound    Int       var randomFromRange  Bound           get               var offset   0             if lowerBound  lt  0                   offset   abs lowerBound                            let mini   UInt32 lowerBound   offset              let maxi   UInt32 upperBound   offset              return Int mini   arc4random uniform maxi - mini   - offset                    let n    -1000     1000  randomFromRange print n    Or this a bit  hacky  solution to support open and closed intervals    extension CountableRange where Bound    Int       var randomFromRange  Bound           return uniformRandom from  lowerBound  to  upperBound           extension CountableClosedRange where Bound    Int       var randomFromRange  Bound           return uniformRandom from  lowerBound  to  upperBound - 1           func uniformRandom from  Int  to  Int  - gt  Int       var offset   0     if from  lt  0           offset   abs from            let mini   UInt32 from   offset      let maxi   UInt32 to   offset      return Int mini   arc4random uniform maxi - mini   - offset     Not sure if there is a way to add property to both types of intervals simultaneously

User · Answer

I modified  DaRk- -D0G s answer to work with Swift 2 0      Arc Random for Double and Float    public func arc4random  lt T  IntegerLiteralConvertible gt   type  T Type  - gt  T       var r  T   0     arc4random buf  amp r  sizeof T       return r   public extension Int               Create a random num Int      param  lower number Int      param  upper number Int      return  random number Int     By DaRkDOG            public static func random  lower  Int   upper  Int  - gt  Int           return lower   Int arc4random uniform UInt32 upper - lower   1             public extension Double               Create a random num Double      param  lower number Double      param  upper number Double      return  random number Double     By DaRkDOG            public static func random lower  Double  upper  Double  - gt  Double           let r   Double arc4random UInt64     Double UInt64 max          return  r    upper - lower     lower         public extension Float               Create a random num Float      param  lower number Float      param  upper number Float      return  random number Float     By DaRkDOG            public static func random lower  Float  upper  Float  - gt  Float           let r   Float arc4random UInt32     Float UInt32 max          return  r    upper - lower     lower

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var rangeFromLimits    arc4random uniform   UPPerBound - LOWerBound      1     LOWerBound

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Swift   var index   1   random     6

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hope this is working  make random number between range for arc4random uniform     var randomNumber   Int arc4random uniform 6   print randomNumber

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Since Swift 4 2   Int           public static func random in range  ClosedRange lt Int gt   - gt  Int     public static func random in range  Range lt Int gt   - gt  Int     Used like   Int random in  2   10

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The answer is just 1 line code   let randomNumber   arc4random uniform 8999    1000   for 4 digit random number let randomNumber   arc4random uniform 899999999    100000000   for 9 digit random number let randomNumber   arc4random uniform 89    10      for 2 digit random number let randomNumber   arc4random uniform 899    100    for 3 digit random number   The alternate solution is       func generateRandomNumber numDigits  Int  - gt  Int      var place   1     var finalNumber   0      var finanum   0      for var i in 0    lt  numDigits           place    10         let randomNumber   arc4random uniform 10                   finalNumber    Int randomNumber    place         finanum   finalNumber   10            i    1           return finanum     Although the drawback is that number cannot start from 0

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If You want i create that for random numbers  this is extension of number Int and Double  Float          Arc Random for Double and Float    public func arc4random  lt T  IntegerLiteralConvertible gt   type  T Type  - gt  T       var r  T   0     arc4random buf  amp r  UInt sizeof T        return r   public extension Int               Create a random num Int      param  lower number Int      param  upper number Int      return  random number Int     By DaRkDOG            public static func random   lower  Int   upper  Int  - gt  Int           return lower   Int arc4random uniform upper - lower   1            public extension Double               Create a random num Double      param  lower number Double      param  upper number Double      return  random number Double     By DaRkDOG            public static func random  lower  Double  upper  Double  - gt  Double           let r   Double arc4random UInt64     Double UInt64 max          return  r    upper - lower     lower         public extension Float               Create a random num Float      param  lower number Float      param  upper number Float      return  random number Float     By DaRkDOG            public static func random  lower  Float  upper  Float  - gt  Float           let r   Float arc4random UInt32     Float UInt32 max          return  r    upper - lower     lower           USE    let randomNumDouble   Double random lower  0 00  upper  23 50  let randomNumInt   Int random lower  56  upper  992  let randomNumInt  Float random lower  6 98  upper  923 09

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Swift 3 4   func randomNumber range  ClosedRange lt Int gt    1   6  - gt  Int       let min   range lowerBound     let max   range upperBound     return Int arc4random uniform UInt32 1   max - min      min

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According to Swift 4 2 now it s easily to get random number like this  let randomDouble   Double random in  -7 9   12 8   let randomIntFrom0To10   Int random in  0    lt  10    for more details check this out

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I successfully accomplished creating a random number using the following code   var coin   arc4random uniform 2    1   Hope this can help you

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In swift     This is inclusive  calling random 1 2  will return a 1 or a 2   This will also work with negative numbers       func random min  Int    max  Int  - gt  Int           guard min  lt  max else  return min          return Int arc4random uniform UInt32 1   max - min      min

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Quite a few good answers  but I just wanted to share my personal favourite Swift random number generation function for positive integers   Swift 2  func randomNumber range  Range lt Int gt    1   6  - gt  Int       let min   range startIndex     let max   range endIndex     return Int arc4random uniform UInt32 max - min      min     Swift 3  Here s a quick update for Swift 3 and  as a bonus  it now works for any value type that conforms to the SignedInteger protocol - much more convenient for core data applications that need to specify Int16  Int32 etc  As a quick note  if you really need it to work on unsigned integers as well  just copy the entire function then replace SignedInteger with UnsignedInteger and toIntMax   with toUIntMax     func randomNumber lt T   SignedInteger gt  inRange range  ClosedRange lt T gt    1   6  - gt  T       let length    range upperBound - range lowerBound   1  toIntMax       let value   arc4random   toIntMax     length   range lowerBound toIntMax       return T value      Swift 4  Thanks to the removal of toIntMax   in Swift 4  we now have to use a different means of converting to a common integer type  In this example I m using Int64 which is large enough for my purposes  but if you re using unsigned integers or have an Int128 or Int256 custom type you should use those   public func randomNumber lt T   SignedInteger gt  inRange range  ClosedRange lt T gt    1   6  - gt  T       let length   Int64 range upperBound - range lowerBound   1      let value   Int64 arc4random      length   Int64 range lowerBound      return T value      One more  for the total random-phile  here s an extension that returns a random element from any Collection type object  Note this uses the above function to generate its index so you will need both   extension Collection       func randomItem   - gt  Self Iterator Element           let count   distance from  startIndex  to  endIndex          let roll   randomNumber inRange  0   count-1          return self index startIndex  offsetBy  roll             Usage  randomNumber     returns a random number between 1 and 6   randomNumber 50   100    returns a number between 50 and 100 inclusive  Naturally you can replace the values of 50 and 100 with whatever you like   Swift 4 2  Alas  my best StackOverflow answer has been rendered obsolete at last  You can now use simply Int random in  1     6  to generate a random number in a given range  Also works for other forms of integer and floating point number  Collection types also now provide shuffle   and randomElement   functions  There is therefore no longer any need for fancy randomisation functions unless you want to use a specific randomiser type

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Edit  Swift 4 2  provides this now    100   200  randomElement       It   s idiomatic to me to extend Range   public extension Range where Bound    Int       var random  Int           return lowerBound   Int arc4random uniform UInt32 upperBound - lowerBound             public extension ClosedRange where Bound    Int       var random  Int           return lowerBound   Int arc4random uniform UInt32 upperBound - lowerBound   1              In use   let foo    100   lt 600  random

[range] How does one make random number between range for arc4random_uniform()?

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